Wait, I is worse than X-2? I'm contesting that because X-2 was awful beyond awful.
In terms of doing new and interesting things for the time and setting standards and suchlike, I blows X-2 so far out of the water that Yuna has good empirical reasons to believe water is a myth. But, hell, I recall managing to get a few moments of fun out of X-2 over the course of the game, and at least it was pretty to look at. Had some quality music in places. It did have characters, although I don't remember any of them being particularly likable. All of that's more than I can say for FFI's original release, whose only value I can endorse is legacy. Which is huge, don't get me wrong.
I'd rather live in a world that never had X-2 than I, but I'd rather
play X-2 than I.
Re: Villains
Yeah, that's the appeal in Kefka. He's a one-off in the series, in the regard SalmonGod's describing, I think. He's not a character, he's just a force of nature. He's a motivator for the plot, sure, and opposition to him is largely what unites the heroes, but he's basically just a plot device. He doesn't need development - even "He lost his mind in an early Magitek experiment", which is basically his entire backstory, is totally unnecessary to understanding his place in the game, which is why it's a throwaway line from an NPC in a building you'll never enter unless you're just exploring.
One of the reasons I like less some of the other villains in the series is that they have basically the same role in the story, but the narrative doesn't very effectively embrace it. It often felt kind of piled on. Kuja's probably the best they ever did at blending a character with a catastrophe, but many of the games have relied on the primary antagonist also being the world-ending threat personified, and it usually doesn't work out so well if you try to add in character development. I don't think they nailed the villain-as-character until XII (which is why it's so dear to me, actually), with Vayne, but they definitely did do some fairly good secondary antagonist characters before that (I've got good memories of Seifer).