All I'm hearing from DocFrance and Doom...dude (sorry, forgot your name) is nothing more than BLASHPHEMY!! IF YOU DO NOT THINK SEPHIROTH IS THE GREATEST VILLAN IN FF THEN YOU MUST BE EXILED TO THE FAR REACHES OF KNOWN SPACE! ....sorry..i just think you guys are wrong....<.<...>.>...
(I'm saying this a lot today) Oh...my...god...

Very funny DocFrance, but you just assume the reason that everyone likes Sephiroth is that he has a big sword. The reason I like him is because he is 1. Evil, 2. always so eeriely calm, and 3. he is one tough S.O.B., now ive played most every RPG out there and i have to say that Sephy takes the cake. You're just trying to be differant just to be one that does not conform, well doing what you want is not conforming to anyone but you. Does that help any?
1. How is he evil? You want to see pure evil, try Luca Blight or hell, even Kefka. Now, as Doomy and Doc said, Luca Blight(or Kefka) fanboys aren't much better than Sephiroth fanboys, but at least the former were actually evil. The reason I, personally, like Sephiroth is that he's a sympathetic villain. You're meant to feel pity towards him, if you actually have a freakin' clue what's going on during the game. You're also supposed to be somewhat in awe of him, not because of his "evilness," but because of his apparent limitless knowledge.

2. He's eerily calm because he's INSANE. He literally lost his mind. He doesn't bottle his emotions; he's just quite literally incapable of them. Remember when he tells Cloud "stop pretending that you're sad"? That's because he literally doesn't think sadness is a plausible emotion. Again, you're meant to pity him for that.

3. Tough S.O.B.? He's one of the eesiest bosses in any RPG ever.

You're just a fanboy who likes him because of his looks. Yes, Sephiroth is very much an "overrated prettyboy."

I'm just saying Luca's far better at playing the deranged lunatic than Kefka is. His, erm, brother-in-law was a better antagonist, in my opinion. So was the, uh, Masked Bishop.
Agreed. Luca's much better than Kefka. Luca, admittedly, is the best "pure evil" villain in any RPG. However, there are much better overall villains(especially from Lunar SSSC).

EDIT:

Because you still think Sephiroth is the best. Clearly your horizons are not very broad
Absolutely. Do yourself a favor and play Suikoden II and Lunar SSSC. Hell, and FFT.