I only started watching dramas since a short period ago, before I watched only anime but that changed after I found the drama adaption of one of my favorite animes.
I prefer Japanese dramas, I think it's because I'm more used to the language, but I don't discriminate on chinese , korean, taiwanese dramas, etc.
My favorite dramas are Historical one, time-traveling dramas are even better. I've Always liked history and you can learn a lot from those historical dramas  ^_^
I haven't watched so many dramas but the list will probably grow much longer ^_^