This is hard..But this is m top 3.

1. Cruel City.---until now nothing beat this one.
2. Fated To Love You(Korean Version)
3.Chuno and Queen Seon Duk



ughh.. but I also love Beautiful Mind, Its okay that's love and Tree With Deep Roots.. :(
1.Kill Me, Heal Me
2.Beautiful Mind
3.Hello Monster
1. Boys Over Flowers
2. To The Beautiful You
3. Marriage, Not Dating
Scarlet Heart Ryeo because it's just the best drama ever known
Healer
Moorim School
King2Hearts 
Gap Dong
Healer
Incomplete life, Signal and healer.
W- One of the very few dramas that pulled me in right from the start
White Christmas- Had me on the edge of my seat the whole time
My gf is a gumiho- Perfect fantasy romance drama
I would add Goblin, but it totally depends on the ending for me :)
1 . SIGNAL
2. MISAENG(incomplete life)
3.CRUEL CITY(heartless city)
Kill Me Heal Me is very close with my top 3.
All my faves have excellent plot, suspense, great acting and directing.
I recommend  to all Kdrama fans to watch them if they have not seen them yet.
1. Bad Guys (10)
2. It's Okay, That's Love (9.5)
3. Healer (9)

I found all three these dramas almost-- or even truly perfectly done; the plot, the acting, the characters were amazing, the storyline exciting and addicting, and the dramas made me feel a lot of emotions. 
1. misaeng
2. healer
3. age of youth
1. Healer 
2. Queen In Hyun's Man 
3. Kill Me, Heal Me
1- Gap Dong (2014, TvN)
2- IRIS (2009, KBS2)
3- Doctor Stranger (2014, SBS) 

I have no idea why, cuz it's been some time since I watched them. But I remember of my feelings when I finished watching them! hahahaha I love them, I must re-watch some time around :P 
1. Heartstrings
2. Pinocchio
3. The heirs
1. Faith
2. Secret Garden
3. You're Beautiful 
4. Rooftop Prince
5.Gu family book
6.Scarlet Heart

I know I have to pick 3...but I can't do that...so these are my top 6 ..Not in order