Kefka is awesome in that what he does is truly dispicable, and you can tell by his dialogue he relishes in all the pain and suffering he causes.

He may be far from an in depth villain, but he succeeds in a place most villains fail, you want to beat him. As I player, I felt the need to put an end to what he was doing.

Villains like Sephiroth, Ex-Death, and really all FF Villains outside of Kefka and Kuja fail to capture this feeling. Sure, in context of the story you feel they need to fall, but outside of these two I never personally felt the need for their defeat.

That is where Kefka excels best