I don't care about the whole 'Kefka is better than Sephiroth!!11' thing because it's just some strange way of feeling better than anyone who likes Sephiroth anyhow.
I like Sephiroth. He isn't my favorite villain. There are obviously better villains. But I don't think he's a bad villain. He was pretty scary, and mysterious, so he's just your typical villain, I suppose. I liked how the group chased him (or a projection of him, whatever) around everywhere, a different way of following the villain than in most of the other FF games. (Of course, you don't know what on earth he's planning for half of the game, thus adding to his mysteriousness.)
And, well, I wish I had that sword.
Furthermore, it makes me giggle when people complain about lots of people declaring that Sephiroth is great, when more people go on about Kefka than anything.