It's funny how everyone loves Sephiroth
He's got to be one of my favourite villains, too. Kefka was great, as was Edea, although I agree about Kuja and Necron, though I'd add Seymour to the list of slightly disappointing bad guys. Vayne wasn't great, either (Gabranth or Cid would have been better, in my opinion). I liked Hojo - especially now that he features in two games I've played - although I wasn't fond of Scarlet. The slap fight on the end of the Junon Cannon was funny, though! I liked Heideggar instead (for comedy value).
And no - the Turks couldn't be called villains! Especially since they help out so much in Advent Children.
Rufus gave it a good try, though.