Wow this is tough as we have more than 5 favourites Korean drama right?  Anyway, to join the fun here are my top 5 Kdrama of all time in random:

1.  Empress Ki - splendid and grandeur, JiChangWook's acting is mind-blowing and mind-boggling!

2.  Bridal Mask - powerful acting of the two main leads, the best action drama with epic in proportion!

3.  Healer - perfect in all department, the best FRUITATION OF LOVESTORY in a drama from beginning to end.

4.  Sungkyunkwan Scandal - the best cross-dressed gender drama that I have watched.  The 4 main leads are its ACES (Park Minyoung, Song Jongki, Park Yoochun and Yo Ah In)

5.  1% of Something 2016 - light, good-feel, romantic, sweet, love story is simple but relatable and heart fluttering.  The leads are just awesome and refreshing and should I say the best kisses in all dramas are here?

This is an awesome discussion and thread!
1) Kill Me Heal Me
Beautiful and extremely accurate take on the psychiatric world as well as mindblowing acting from Ji Sung.

2) Reply 1988
I cried repeatedly. And got PTSD. So yeah.

3) Beautiful Mind
THIS WAS SO GOOD WTH IT WAS AMAZING JANG HYUK I LOVE YoU

4) Pinocchio
SO inspirational omg

5) Weightlifting Fairy Kim Bok Joo
Just super super super cute love story that's gonna make you cry yourself to sleep thinking about how you're lonely and single 
1. Signal
2. Healer
3. 1% of Something
4. Defendant
5. Weightlifting Fairy
1.GOBLIN: I loved everything about this drama, the plot, the cast, the cinematography, everything
2.SCARLET HEART RYEO: Such an intense drama, the male lead it really a bad guy, unexpected finale
3. DESCENDANTS OF THE SUN: this was the first drama that made me cry...ALOT  loved every character even the villane, the ost is amazing too
4.SHOPPING KING LOUIE: althounght i almost dropped it at the 3rd ep, it's such a cute drama, i loved the both leads, it made me laught alottt
5.HEARTLESS CITY: is an intense drama, jung kyunh ho looks amazing, the plot is really good, but it's not a happy ending
Goblin 
good doctor 
healer 
signal 
reply 1988
healer (2014)
falling for innocence (2015)
w (2016)
strong woman do bong soon (2017)
kill me, heal me (2015)
1) A gentlemans dignity 
2)goblin (2016-2017
3)kill me heal me
4)the lover (2015)
5)strong woman do bong soon (2017)


or just check my fav dramas/movies list :) 
1. Drinking Solo - there was never a single moment i feel bored because the plot is good and the characters are all very relatadable! 
2. Signal - do i even have to explain? 
3. Weightlifting Fairy Kim Bok Joo - this is literally the cutest drama i have ever watched! I've got post-drama sydrome thanks to this drama. It's really good and again, there's no moment where i feel bored because the storyline is very consistent (school theme drama)
4. Empress Ki - i love Ha Ji Won's acting here and the story plot is very solid. 
5. Cheer up - super underrated show but i really like it, it's a school theme drama
1. HEALER
2. STRONG WOMAN DO BONG SOON
3. WEIGHTLIFTING FAIRY KIM BOK JOO
4. W TWO WORLDS
5. YOU WHO CAME FROM THE STARS 
stairway to heaven
winter sonata
dong yi
yi san
jewel in the palace
it's really really hard to stop here...
in my database of what i have watched from South Korea i have 27 ranked #1 of which 17 are drama's and 10 are movies.  the 2nd rank shows are ALMOST as good as the first rank shows.  To only show you 5 out of all these does injustice to the rest!  then there's the dozens or hundreds i have not ranked yet!  What i find unusual and sad is no one seems to rank the older drama's, the true classics that started it all.  I seem to think very few modern drama's come close to those epic classics.  The other thing i have problem with is trying to rank historicals in the same list with the others.  it's like ranking apples and oranges.  they kind of deserve their own list.  Well i gave out 5.. but it means nothing because the ones i left off are as good as those 5.
@fryyyy You can share those dramas here. It's fine since you mentioned that they're really good. It'll help those who'll see this forum to have more options. I just said to list 5 to make things organized. But you can go ahead and share more. I'm looking forward to lots of dramas to watch! :)
Ex-Girlfriend Club
Weightlifting Fairy Kim Bok Joo
Marriage Contract
W
The Promise
W, Signal, Goblin, You Who Came From the Star, It's ok that's love.
  1. Road Number One - Now I know this is not a common drama to be first, however I think to me this was one of the most beautiful yet touching drama's I've watched. (10/10)
  2. Moon Lovers: Scarlet Heart Ryeo - I did believe this drama had a beautiful scenery, acting was good and IU was in it (probably that might have been one of the reasons for a high score either :p (9.5/10)
  3. Six Flying Dragons - A drama which contained a lot. Romance, history, drama, revanche. Even though I usually do not watch dramas from 50 or up, I must say that there was no single episode that bored me. (9.5/10)
  4. Descendants of the Sun - Now I know a lot of people are fan of it or not, but I kinda loved this drama. It contained humour, romance and yet drama. (9/10)
  5. Innocent Man - Great story of a guy giving up everything for someone and being betrayed by her in a later stage. (9/10)
Yet I have to watch plenty of other dramas, so I am not entirely sure my list would be like this next year :)