I realised I know very few of the older ones when it comes to dramas (not movies). Most lists also only include the more recent ones or it's mostly movies.

Uff i guess it's because the genre for dramas wasn't popular until recently.

Found some old ones that sound interesting:

Keizoku  (jdrama)

Damo (kdrama)

Liar Game (jdrama)

Maou (jdrama)

Tree With Deep Roots (kdrama)

Gap Dong (kdrama)

Ghost (kdrama)

City Hunter (kdrama)

Two Weeks (kdrama)

I hear your voice (kdrama)

God's Gift 14 Days (kdrama)

Soredemo, Ikite Yuku (jdrama)

But honestly, i have no idea if any of them are good as all of them are still on my watchlist. I did see praise for many on this list.

Thank you! Yeah I agree before Netflix it was also mainly OCN which broadcasted this kind of dramas and from what I can find they only had 2 dramas before 2010. So probably indeed there just aren't that many before mid-2010s. 

I've watched Ghost, I hear your voice and Liar game (the Korean remake).

Ghost is good, the second half drags a bit, but overal it's solid drama. I really liked Mad Cow who was my first favorite crazy detective. He's a bit annoying in the beginning, but he grows on you.

I hear your voice is great too and the same for Liar game (but at least in case of the Korean remake it's possible that you can't stand the main character, it's how her character is supposed to be, but yeah it can be annoying to some).

Unfair 

Koshonin

BOSS

Mr. Brain

God's Quiz

Sign

Special Affairs Team TEN

I'm surprised no one mentioned History of the Salaryman.  I love the ML and the FL so much! They have great character development.

Thank you all for the suggestions