Kefka's actions may have been surpassed by those of later villains, but none of them in the FF series did it with as much style. (Roger Bacon of Shadow Hearts and Luca Blight of Suikoden II are the only ones I've encountered who have comparable style, actually).

of the FF villains, Kuja is the one who comes closest to matching Kefka, but he doesn't have brilliant lines like "You sound like chapters from a self-help booklet," so Kefka still wins.