In general, I never re-watch dramas that I love, but I filled out this list by imagining which 10 dramas I'd happily sit through again. All of these not only kept my attention during every scene, but also stayed with me for weeks after I finished watching.

Fight My Way
Secret Love Affair
Healer
Crash Landing on You
One Spring Night
It’s Ok to Not Be Ok
Mr. Queen
The Smile Has Left Your Eyes
King2Hearts
Seven Days Queen

I struggled a bit with coming up with my favorite ten, because although I've ranked some shows higher, these have a lingering feel to them or of high re-watch value.

Healer
Reply 1997
I am not a Robot
Reset
Chief Kim
Bloody Romance
Chicago Typewriter
Melo is My Nature
The Day of Becoming You
I Remember You

I somehow would like to include Strong Woman Do Bong Soon on the list as it is my favorite romance of all, but unfortunately the rest of the drama is a drag. But I've watched it three times.

My drama watching has all but dried up since becoming a parent so this is all making me wistful for the shows i haven't seen, hurriedly writing them down for whenever i have time again.

My list. These all feel of a certain time:
-- My Daughter Seoyoung
-- Flowers For My Life
-- Shut Up Flower Boy Band
-- The Light in Your Eyes
-- Queen Inhyun's Man
-- My Girl
-- Ruler of Your Own World
-- Oh My Ghost
-- Another Oh Hae Young
-- Miss Korea

I certainly haven't watched enough Korean dramas to have a "10 Best" list, but - in no particular order - these are the ones that I have found worth re-watching:

- On the Verge of Insanity (of course)
- My Ahjusshi (another obvious one)
- Forest of secrets 1 and 2 (yet another obvious one)
- Angry Mom (my intro to the darkly madcap world of writer Kim Ban-di)
- Awl ("It's not about protecting helpless saints from powerful evil people. For petty powerless people, we fight petty powerful people.")
- A New Leaf (another show about fighting on behalf of the powerless)
- Resurrection (one of the most gripping plots ever written, and starring pre-scandal Uhm Tae-woong as a vengeful twin)
- Conspiracy in the court (I'm not a sageuk fan, but this really is one of the most perfect dramas ever made)
- The Chaser (not the film but the drama starring Son Hyun-joo)

What a great list of future recommendations!

My list (why only 10?) Theses are the ones (in no particular order) I return to for comfort...

1. Healer
2. One Spring Night
3. A Business Proposal
4. Weightlifting Fairy Kim Bok Ju
5. Vincenzo
6. Coffee Prince
7. Crash Landing on You
8. Touch your Heart
9. You from Another Star
10. Our Beloved Summer

Honourable mentions: Encounter/Boyfriend, Hotel Del Luna, Descendants of the Sun, My Roommate is a Gumiho, It's OK not to be OK, Suspicious Lawyer

Top 10 dramas that grabbed my heart and lingered/ all time faves

🌷Jealousy Incarnate (Don’t Dare to Dream) - first time to rewatch this one in full this year and it was double the enjoyment

🌷Oh Hae Young Again
🌷Just Between Lovers
🌷I Am Not A Robot
🌷Radiant Office
🌷A Piece of Your Mind
🌷Hospital Playlist
🌷 Mad for Each Other
🌷Happiness
🌸 My Liberation Notes (hopeful for this one!)

Jdramas
🌷Why I Dress Up for Love
🌷 We Married as a Job

Other loves ♥️
My Ahjusshi
My Unfamiliar Family
Be Melodramatic
Healer
Because This Life Is Our First
Something About 1%
She Was Pretty
Do You Like Brahms
Mystic Pop up Bar
Still 17
Run On
MrQueen
Move to Heaven
Misaeng

Difficult to choose just ten, but here it is in no particular order:

1. Healer
2. Coffee Prince
3. Crash landing on you
4. My Mister
5. Romantic Doctor Kim (both)
6. Extracurricular
7. Bad Guys
8. Go to You when the weather is fine
9. Red Sleeve Cuff
10. One Spring Night

Still waiting for the ending of My Liberation Notes, but it probably will make the list in future.

My top 10 kdramas
Flower of evil
Healer
The devil judge
Doom at your service
The Master's Sun
Hello Monster/Remember me
Crash Landing on you
Happiness
Psychopath diary
Suspicious partners

top 5 Cdramas
Killer and Healer
Legally romance
City of streamer
Love at night
I am the years, you are the star

Wow, this is a LOT harder than I thought it would be. Noticed that I tend to enjoy dramas that allow women to have a brain. Whittled this list down by what I would happily re-watch, anytime. There is an order because I realized the last few were hardest of all to choose.
My Mister/Ahjussi
Miseang
Forest of Secrets/ Stranger
Be Melodramatic
I Am Not A Robot
Hot Stove League
Because This Is My First Life
Bossam: Steal the fate
Rookie Historian
Hotel del Luna

Reply 1997
Reply 1988
Hello monster/I remember you
Racket boys
A poem a day/you who forgot poetry
Pinocchio
Because this is my first life
Circle
Good manager/chief kim
The guest

Reply 1988
Another Miss Oh
Six Flying Dragons
My Liberation Notes
Misaeng
Valid Love
It’s Okay That’s Love
Secret Love Affair
Memorials
Greatest Love

It's fun to compare my current list with what I put down in Dec for the bean count. Here's the latest - I never thought My Mister would get displaced but I am so fascinated by MLD! Have already rewatched the 1st 10 eps waiting for the last 2. I do hope it doesn't crumble at the end. I actually hated Another Miss Oh -it's 38 out of a total 39. SKY Castle is dead last.

1. My Liberation Notes
2. My Mister
3. Reply 1988
4. Misaeng
5. It’s Okay to Not Be Okay
6. One Spring Night
7. Stranger
8. Touch Your Heart
9. A Business Proposal
10. Romance is a Bonus Book

I also love the next 10 on my list, just slightly less!
11. Crash Landing on You
12. Hospital Playlist 1
13. Stranger 2
14. Signal
15. Familiar Wife
16. The King’s Affection
17. Oh My Ghost
18. Life
19. Something in the Rain
20. Hometown Cha-Cha-Cha

Can I make 3 top 10? lol I feel so bad for my other favorite dramas :(
...but I'll try (the order means nothing, except for the first and second position):

Reply 88
Flower Boy Next Door
Be Melodramatic
Misaeng
Shopping Wang Louie
Good Doctor
Love Affairs in the Afternoon
Fight For My Way
Be My Dream Family
Sweden Laundry

Shows that I would consider for my list if they were finished:
It's Beautiful Now
My Liberation Days
Showtime

Adding my list:

1. Extraordinary You
2. Our Beloved Summer
3. 25-21
4. Happiness
5. Hospital Playlist
6. Reply 1988
7. It's Okay not to be okay
8. Live Up to Your Name
9. Healer
10. Because This Life is My First

My other loves: Fight My Way, W-Two Worlds, I Remember You, Age of Youth, My Girl, Descendants of the Sun, Vincenzo, Signal, Full House

I don’t think I can only select 10 of them because all of these grabbed me and never let go: (in no particular order)
1. Forest of Secrets 1
2. 2521 (and I absolutely LOVED the ending, no apologies)
3. Another Oh Hae-young
4. Romance is a Bonus Book
5. Misaeng
6. Hospital Playlist 1
7. Live Up to Your Namr
8. Healer
9. Coffee Prince
10. Ojakgyo Brothers
11. My Husband Mr Oh
12. My Unfamiliar Family
13. Descendants of the Sun
14. I’ll Find You When the Weather is Fine
15. Weightlifting Fairy Kim Bok-Joo
16. Romantic Doctor 1-2
17. Yongpal

Honorable mentions: Goblin, The King, Goong, among others.

1. W--Two Worlds
2. Crash Landing on You
3. I Hear Your Voice
4. Pinocchio
5. Happiness
6. Brilliant Legacy
7. Healer
8. Master's Sun
9. Shopping King Louie
10. Mother

Honorable mention (the above are all Korean, which is mostly what I watched, but I did love these two Chinese dramas as well):

Go Ahead
Reset

Ok here goes
MY Mister
Just Between Lovers
The Red Sleeve
Healer
Descendants of the Sun
It's Okay To Not Be Okay
Dr. Romantic -all of them
Reply-all of them
Hospital Playlist
Stranger -both of them
my love from another star
City Hunter

These are the K-dramas which truly grabbed me and won’t let go. By this I mean the ones that come to mind, where I specifically remember specific scenes.

GOBLIN: THE GREAT AND LONELY GOD was simply an amazing exploration of life and death.

The recently completed Sageuk LEE BANG-WON: KING OF TEARS was unique. I hope that this writer continues to produce screenplays because this one absolutely channeled Shakespeare: All of the tragedies in this historical drama stem from character flaws and the overarching theme of our title character’s descent into paranoia was beautifully executed.

I love comedy and so two of my top ten are WELCOME TO WAIKIKI and PEGASUS MARKET.

Good romcoms are my thing and so I have several:

BECAUSE THIS IS MY FIRST LIFE, which gave us 14 episodes of Shakespearean insights before fizzling in the last two episodes- but those fourteen episodes are the very best.

1% OF SOMETHING which was a remake of 1% OF ANYTHING- both are really good. I would like to think that 1% OF SOMETHING is simply better for being more polished and even more perfectly cast.

BUSINESS PROPOSAL, even though it too fizzled at the end- but still before that we had fourteen episodes of delightfulness and the final episodes were not awful- just flat compared to what went before. Now that I am two thirds of the way through the webtoon I can actually see some earlier mis-steps which would have avoided the disappointments of the final two episodes- such as the reveal that Sung-hoon, Secretary Cha, really is Grandpa’s other grandson: As Grandpa tells Chairman Jin- he is even on Grandpa’s family register.

WHAT’S WRONG WITH SECRETARY KIM? Is hard to beat, even if the SML is appalling.

I love weekenders so two of my all time favorite dramas are ONCE AGAIN and MY FATHER IS STRANGE. I also find myself going back to watch the romance of the golfer couple in FIVE CHILDREN, which would also be in my top ten except that the main couple had no chemistry at all. Another runner-up is actually a daily: BE MY DREAM FAMILY

I’LL COME TO YOU WHEN THE WEATHER IS NICE is simply a wonderful drama. I realize that this makes eleven rather than ten but I just cannot keep it off my list. If it had been twelve instead of ten I would have added SHOPPING KING LOIUE.

Even my favorite shows have flaws, which have actually taught me things about K-drama in general. For instance, the need to fill out a set number of episodes that a writer is committed too has sometimes been the obvious reason for awkwardness in ending a show. My favorite example of this is the truncation of the story arc that I call “Maknae and the Chairman” in the weekender MY FATHER IS STRANGE: You could actually picture what we should have seen but were not given.

In no particular order:
1) Crash Landing on You
2) Hotel de Luna
3) Start-up
4) Chicago Typewriter
5) A Korean Odyssey
6) Live up to your name
7) Master's Sun
8) Sungkyunkwan Scandal
9) Coffee Prince
10) Good Manager Kim

Honorable mentions:
W - Two worlds apart - one or two twists too many, but until then, what a ride.
The Bride of Habaek - I think the bait-and-switch forgrounding of the more mundane story-beats at the expense of the supernatural elements as well as the weirdly passive, often seemingly idiot-ball carrying hero are actually features not bugs, but I know I'm in the minority here.
Hyena - mileage may vary with regard to the redeemability of the anti-heroine here; I do like a bit of moral ambiguity and flawed protagonists, and the central couple is super hot.

Making this list hurt me. I’ve been watching dramas for so many years and so many shows have grabbed me that it’s difficult to leave some out. And then just when I think I assembled a list, I end up remembering one that there’s no way I can leave out. This was a mess.

So uhh, there’s my list. This is NOT in order (I could never).

1. Coffee Prince
2. Chicago Typewriter
3. Queen In-hyun’s Man
4. Just Between Lovers
5. My Ajusshi
6. Oh Hae-young Again
7. Six Flying Daggers
8. Gaksital
9. Healer
10. Arang and the Magistrate

Oh my. This will be quite the challenge. 😂
Here's mine:
1. Hospital Playlist
2. Twenty Five, Twenty One
3. Prison Playbook
4. Another Oh Hae Young
5. Go Back Couple
6. Something About 1% (2016)
7. A Business Proposal
8. Goblin/Mystic Pop-up Bar
9. Because This is My First Life
10. Life on Mars

Runner-ups: Pinocchio, Run On, You Are My Spring, Our Beloved Summer, Be Melodramatic, Bad Guys, Romance is a Bonus Book, Her Private Life, Age of Youth, Kill Me Heal Me, Yumi's Cells

Huh. Slice-of-life really gets the bigger chunk of my top list. 😅

Edit: I had to delete my previous comment 'coz HOW COULD I FORGET GO BACK COUPLE??? Ugh. Still my favorite of Jang Nara' s. 😍

This is even hard for me, and I've been watching kdramas for only 1 1/2 years. So I tried not to overthink and put down my favorites at this moment...
* Coffee Prince
* Goblin
* Healer (watched on recommendation from Dramabeans, and I totally agree...)
* I Remember You (Dramabean's hidden gem)
* Rookie Historian Goo Hae Ryung (because this was my very first kdrama, and I watched it twice right away - so this one grabbed me and didn't let me go from dramaland!)
* Doom At Your Service (because Seo In Guk, and the first drama I watched live, and I still love it)
* Reply 1997
* Strong Woman Do Bong Soo
* Vincenzo
* Business Proposal

Honorable Mentions: Crash Landing on You, Move to Heaven, Master's Sun, Happiness

OK--I'll play. Here's my list, in no particular order:

1. Chicago Typewriter
2. My Mister
3. It's Okay to Not Be Okay
4. My Lovely Sam Soon
5. It's Okay, That's Love
6. Defendant
7. 100 Days My Prince
8. Coffee Prince
9. Melo is My Nature
10. Encounter (I know, I know . . . but it hit me at *just* the right time)

Let's see, let's see. I feel like I'm going to begin this list thinking I don't have a top 10! And it's going to end with because I have a top 175. Let's do this thing.
This is mostly in no particular order
1. Fight for My Way
2. It Started with a Kiss/TKA
3. Kiss Me
4. Chicago Typewriter
5. Just Between Lovers
6. A Gentlemans Dignity (if you ignore the friend/little sister storyline because it was incredibly poorly done)
7. It's Ok to Not Be Ok
8. The Package
9. Something About 1%
10. Daljas Spring

Honorable Mention:
Pretty Noona would be on this list if the back half didn't suck so INCREDIBLY hard. But it does. And it will always be number one on my most hated dramas and best first handholds list. I have complicated feelings towards this drama.
APAD is a toss up. DB was SO.MUCH.FUN. during that war but also the wrong side won. So it's not on the list.
Lee Min Hos Boys Over Flowers will always be kind of on this list because it was my first drama and it hooked me even though it has its...flaws? Who among us doesn't?!
And Hello Monster. It's awesome. I should rewatch that.

11 dramas :)

1) Do You Like Brahms
2) Search: WWW
3) Be Melodramatic
4) Another Oh Haeyoung
5) Kill Me Heal Me
6) I Can Hear Your Voice
7) Memorials
8) 2521
9) Yumi's Cells
10) Mad For Each Other
11) Because This is My First Life

Honorable mentions:
1) Suspicious Partner
2) Mr Queen
3) Pinocchio
4) Sassy Girl Chunhyang
5) Nice Guy (love to hate the pain)

Top 10

1. NIRVANA IN FIRE🔥🔥🔥🔥
2. Mr. Sunshine
3. All about eve
4. Chief Kim
5. Tree with deep roots
6. 1% of something
7. Racket boys
8. Princess Weiyoung
9. Queen InHyun's Man
10. Prison playbook

-city hunter
-pinocchio
-healer
-tunnel
-flower of evil (except last episode)
-touch your heart
-fated to love you
-once again
-kill me heal me
-kingdom
-reply 1997
-personal taste

Top 10? only 10? that's really difficult!
I guess I'll start with the ones that I've watch more than once...
In no particular order but just what pops into my mind when I press "search: shows I've watched more than once"
1) Goong
2) coffee prince
3) shining inheritance
4) W-two worlds
5) Monster / i remember you
6) Faith
7) My Ahjussi
8) My girl
9) Go back spouse
10) 20 again
11) 7 day Queen
12) master's sun

There's plenty more to this list of rewatched... I might add it in the comments section if I can remember them later.

List # 2 (rewatched Chinese dramas)
1) Scarlet Heart
2) Nirvana in Fire
3) Nirvana in Fire 2
4) Legend of the condor heros
5) return of the condor heros
6) The Untamed
7) Autumn's concerto
8) It started with a kiss
9) inborn pair
10) Love now

and lastly, just a list of dramas that drew me all the way into its story:
1) kill me heal me
2) signal
3) circle
4) chimera
5) Yumi's cell
6) red sleeve cuff
7) sky castle
8) innocent man
9) Bossam steal the fate
10) Mr. Queen
11) Empress's dignity (live watch with Beanies fan wall)
12) a beautiful world
13) smart prison living
14) avenger's club
15) forest of secrets
16) Father is strange
17) kill me heal me
18) oh hae young again
19) chicago type-writer
20) tunnel

Oooh this is a fun prompt! :) Here's my 10+1 extra. Though I think these are my current top faves because I so often find myself still thinking about certain lines, characters, and moments from each of these.

1. My Liberation Notes
2. Misaeng
3. My Ahjusshi
4. Kingdom - Seasons 1 & 2
5. Because This is My First Life
6. Another Oh Hae Young
7. Hospital Playlist Season 1
8. Romantic Doctor Teacher Kim - Season 1
9. Queen for 7 days
10. The Red Sleeve
11. Crash Landing on You

Let's just pretend I can't count and only have ten on this list, 'kay?

1. Just Between Lovers
2. Healer
3. Descendants of the Sun
4. Reply 1988
5. Hospital Playlist
6. W: Two Worlds (minus the last episode)
7. Our Beloved Summer
8. Dear My Friends
9. Twenty-Five, Twenty-One (even though I hated the ending)
10. Fight For My Way
11. It's Okay To Not Be Okay
12. Itaewon Class

If they end well, My Liberation Notes and Red Heart will be added to the list...

In no particular order, here's mine
1.Goblin
2.Mr Sunshine
3.Moonlovers: Scarlet Heart
4.Stranger 1&2
5.Hospital Playlist
6.It's Ok to not be Okay
7.Reply 1988
8.Happiness
9.2521
10.Mr Queen
Honorary mentions include Awaken, Birthcare Centre, Chicago typewriter and Signal

Drumroll…
1. Hotel Del Luna
2. My lovely Sam Soon
3. Healer
4. Chicago Typewriter
5. Mr. Sunshine
6. True Beauty
7. DOTS
8. Beauty Inside (movie)
9. A piece of your mind
10. Crash landing

All have touched my heart in some way or are just so easy to watch again and again.
H. M. To the unforgettable movie A Quiet Dream

Loving these lists and their diversity! For me, in no particular order:
1. Healer - my face breaks out in a smile whenever "Eternal Love" emerges on a playlist...
2. Chief Kim - I could watch Chief Kim being irritating in the "naughty corridor" forever.
3. It's Okay to not be Okay - the drama I consistently wrote essays about on DB cos I loved it so much.
4. Start Up - while it had faults, Halmeoni and Ji-pyeong made me cry buckets and yearn for more of Halmeoni's goodness in the world.
5. Vincenzo - an operatic masterpiece and one of the best ensembles ever. Plus I adore a well-cut suit...
6. Beyond Evil - so tightly paced and plotted. Could. Not. Put. It. Down.
7. Prison Playbook - so many redemption arcs, it's beautiful.
8. D.P. - not sure I will watch it again, but it's message has been burned into my long-term memory and it still haunts me.
9. Misaeng - making a drama about an office so utterly compelling is an achievement of the highest order.
10. Just Between Lovers - never have I wanted to hug a set of characters so much and tell them they're doing well.

So many I left out...

Interestingly when i searched through the comments using control + F (partly to look for new shows to binge on), the real popular ones are:

Healer (most votes so far!)
Crash Landing on You
It's Okay not to be Okay
My Liberation Notes
Hospital Playlist
Reply series

Also, moderately popular are:
Happiness
2521
Business Proposal
Just Between Lovers
Red Sleeve Cuff
My Mister
Oh Hae Young again

Good to know!

Let me share my current faves. This list is not permanent and can always change. I base this on the dramas that left a lasting impression on me.

1. Reply 1988 - I can never get tired of rewatching this show.
2. Our Beloved Summer
3. Queen for Seven Days
4. Kingdom S1
5. Mr Queen
6. You Are Beautiful
7. My Ahjusshi
8. Misaeng
9. Forest of Secrets
10. WFKBJ and SWDBS (i can't choose and I love em both)

Honorable Mention:
The Princess' Man

In no particular order:

1. Signal
2. Another Miss Oh
3. Princess Hours
4. Just Between Lovers
5. Hotel del Luna
6. Our Beloved Summer
7. Age of Youth Season 1
8. Hospital Playlist
9. Reply 1988
10. 25-21

Today's list:
1-Crash Landing on You (my gateway drama)
2-Reply 1988
3-What's Wrong With Secretary Kim?
4-Hospital Playlist
5-My Mister
6-Misaeng: An Incomplete Life
7-Descendants of the Sun
8-Weight Lifting Fairy
9-Healer
10-Red Sleeve
Others: Just Between Lovers (Rain or Shine), Fight for My Way, Encounter, Touch Your Heart, Queen In-Hyun's Man, The Crowned Clown, DP, Navillera, Move to Heaven, Prison Playbook.

Coming at the end of a long thread, I have the luxury of being to write a lengthy post, sure that very few people will read it! First, I want as always to thank @missvictrix for a great idea that lead to a lot of entries. As others have said, thank you as well for all the contributors for some great suggestions--I'll definitely be looking for ones I haven't seen.

I won't make a list, because my perspective is perhaps a too extreme version of @oldlawyer 's view on the flawed nature of kdramas. The length of kdramas (and also, especially cdramas) is both a blessing for writers and a curse. It allows for storytelling choices, but those choices put enormous pressure on the narrative throughout--especially at the end, resolving character development and concluding story arcs.

i think the reason Healer is on so many lists is (besides its charismatic leads) is not that it is at all profound, it is that it balanced romance, action, and political intrigue and resolved them all successfully. (Well, maybe not completely successfully--what was the point of the evil conspiracy, exactly?).

I find it hard to identify a drama that grabbed me and didn't let go, because for me, all kdramas let go at certain points. So you watch them for unique characters, or variations on common tropes, or, in some cases, how they develop more complex themes.

While its very disappointing when kdramas end without some sort of satisfying narrative OR thematic resolution, I imagine it is so difficult as a writer/director, having developed various story lines over 12-20 hours, to think how best to bring them to a close. So I cut the shows a lot of slack for failed endings, or alternatively sagging interest in the middle, or absurd plot twists. But it does mean that no show has really grabbed me in a way that I want to see the whole thing over and over again.

That said, there is one part of almost every romantic drama that I, as a deep thinking, always rational, analytical critic watch over and over again: the love confession!

In order of preference

Reply 1988
My Liberation Notes
Le Coupe de Fourde (chinese)
On the Verge of Insanity
CLOY
Unfamiliar Family
Stranger
Hospital Playlist 1
Something about 1%
Healer

Gosh, this is so hard!

1. Hospital Playlist
2. Reply 1988
3. Stranger / Forest of Secrets
4. Our Beloved Summer
5. The King’s Avatar (Chinese Drama)
6. Mad Dog
7. Healer
8. Coffee Prince
9. Mr. Queen (minus the last 30mins, but the rest is top notch, for me)
10. Going to You at a Speed of 493km (still ongoing, and should wait 'til the ending, but I love the Park twins to bits and pieces, ATM)