Personally, I've never liked Kefka all that much. Yes, he does have a great laugh, but the thing is, he's overly cliched. He's evil, insane, and power-hungry, and I've seen just a few too many villains that fit into that mold to be able to really like any of them. To me, a good villain has to be well-developed as a character, have understandable motivations, and honestly believe that what they're doing is for the greater good. It's more realistic that way--even Hitler believed in his cause and thought he was doing the right thing, after all.

Kefka, on the other hand, just comes across as evil and insane--and not a very well done evil and insane, either. Insane bad guys, if done well, can be both believable and extremely scary. Kefka is neither.

But really, I don't think he's any better or worse than any of the other FF villains. They all tend to more or less fit into the same mold. The Final Fantasy games had the whole Warriors of Light vs. Evil thing in the beginning, and while the stories have gotten way more complex since then, they still have a tendency to show things as stark black and white. And there's nothing wrong with that--you can pull off a perfectly good story that way (and FF does on a regular basis). But personally, I prefer more realistic stories, where everything is in a shade of gray. (Hence my obsession with the Xeno series.)

Anyway, that's just my two cents.