Probably 3 dramas that are in different genres so you have a little variety. However, I somehow ended up choosing dramas that have an element of suspense/where certain things are not revealed until the very end. The genres are still pretty different though and the type of suspense is a little different too.
W - fantasy, romance: lovely relationship the main characters, filled with cliffhangers and unexpected turns - i couldn't wait for a new episode to come out.
Age of Youth - life, friendship, university setting: great characters, heavily focused on characters & their backgrounds rather than 1 plot, good music too.
I Remember You - crime, investigation, psychological: very interesting characters, you don't know who is who and what everyone is capable of for quite some time, MDL has classified this as romance, but it isn't - not in my opinion anyway.