I think City Hunter is the best revenge drama. It's not one of my favorite genres because when it is done badly, it's really bad. But City Hunter is unique in the genre in that it is very thoughtful in regards to the revenge and also it has the best villain because they actually make you feel some sympathy towards him. I also enjoyed Equator Man for the most part, although it had its issues. But the acting was really good and it was very beautiful to look at. Innocent Man too because it is very different than other revenge dramas I've seen, and because of Song Joong Ki (enough said).
I'd avoid A Man Called God and Temptation of an Angel. They are terrible (and even more so because of how their awfulness brings down the great Song Il Kook and Bae Soo Bin, respectively).
