It was brilliantly executed beacuse it created that sense of mystery about the character. It wasn't until later from Cloud's past that we learnt more about Sephiroth, and even then, lots was left out. The overall flow of the games main-storyline is near-perfection as far as i'm concerned. Complicated and quite technical, but definitely way ahead of its time. No game even came close to this level of storytelling on a games console before. That's why it's highly regarded as one of the most influential video games of all time.
You might think it's an overrated game, which is totally fine. But a lot of people who played this game back in 1997 (myself included) remember just how good it was for its time.
I played it back around the time it came out, and I remember being impressed by the graphics, music, and gameplay. The story was very good in parts too, but other than the flashback sequence, it sure as hell wasn't because of the antagonist.
Yeah, Sephiroth became quite a popular figure in video games, but it had nothing to do with the "complexity" of his character.
The notion that Sephiroth was a complex character is laughable unless FF7 is the only form of literature or media you've ever experienced.
Sephiroth was far more interesting than any villian in FF. The evidence speaks for itself. There was lots more development compared to a guy like Kefka - who was simply a complete lunatic. Seph might have completely lost his mind by the end of Disc 1, but he certainly had an agenda before that.
Again, the extent of Sephiroth's development took place in that one flashback. That is all. I have no idea what "lots" of development you're referring to. It really does amount to "mommy issues" and him deciding to destroy the world when he learns about his true origins. What else is there?
Kefka wasn't a perfect character either, nor particularly complex, but he was far more interesting, IMO. It's implied that he changed after being injected with Mag-...something (fuck, can't remember what it's called). He pretended to be somewhat loyal to the Empire until the time was right, and he betrayed the Emperor's trust, killed him, and revealed his true motives. By the end of the game, he had become a full-blown nihilist who destroyed people's lives indiscriminately (including practically every playable character in the game) without flinching, and *succeeded* in bringing about the world of despair and hopelessness he desired. He was opportunistic, power-hungry, ruthless, unpredictable, and flat-out insane. The "Joker-esque" flippancy with which he does evil stuff makes him somewhat unique at first, and then it just adds to his malevolence.
At the very least, Final Fantasy VI, IX, and X (not Seymour) had better villains than VII. And for the record, I don't think Sephiroth "sucked" as a bad guy. He was just nothing special.
-J