You have tons of great things on your list.

I'd prioritize: Cruel City, Secret, and 49 Days
Healer! you are missing out on a great drama!!!
I am really curious about watching this one! People with similar tastes to me seem to either really love it or really hate it so I'm super curious.
The last drama that happened with was Kill Me, Heal Me and I loved that.

You really need to watch Cruel City and Ningen Shikkaku!
D-Day
Queen In Hyun's Man
Reply 1997
Tomorrow With You
Secret
Save Me
Cruel City
Defendant
The Princess' Man
My Beautiful Bride
Jealousy Incarnate
Nine: Nine Times Time Travel
I don't think those are meant for me, but anyway, outside of the ones I've mentioned before you should watch GTO. It's a classic!
You should watch The Crucible, since you said you like 'psychological' and 'real world issues' in your profile.
And I don't know if you would like Queen In Hyun's Man, because it may contain too much love not enough plot (I don't remember much about the plot)
Sorry! stayed on the other page! 

Thanks for your recommendations! I recommend not to miss Chicago Typewriter and Healer.
kar :( you dropped so many good ones , and on your hold list , there are even better dramas , i feel like crying now :D 

i will send you a msg later , and discuss my opinions with you :)
Healer and Moon Lovers: Scarlet Heart Ryeo are must-watch dramas

I also highly recommend Tunnel and Suspicious Partner
RueXie, Thank you! anytime!

Neo, I recommend Signal! It is enthralling!
I recommend finishing Secret and I Remember You outside of the ones I've already pointed out from your PTW
I Recommend Innocent man pointed out from your PTW :)