My top 3:

1. Goblin

And among my favorites but far far behind Goblin...

2. Healer

3. Strong Woman Do Bong Soon

1.Signal 

2.Six flying dragons 

3.Chicago Typewriter

1. It's Okay, That's Love

2. Because This is My First Life

3.A Gentleman's Dignity

Reason: Stories and specially dialogues were so good that i can rewatch them again and again without feeling bored :)

1. W-Two Worlds

2. Goblin

3. Oh My Ghostess

but honestly A Korean Odyssey is messing up my list now so idk what to do *cries*

1.  The Innocent Man 

2. Because This is My First Life

3. Liar Game

This is hard! With no specific order:

Age of Youth

Descendants of the Sun

God's gift - 14 days

(Followed by Signal / Innocent Man / Weightlifting Fairy Kim BokJoo)

1. Moon Lovers Scarlet Heart Ryeo

2. Moorim School

3. Beautiful Days

1. Weightlifting fairy Kim Bok Joo 

2. My father is strange

3. Because this is my first life