Aside from which one was the better (worst?) villain, what if square decided to remake those FF6 and FF7, but switched the main villains in each one... The cold hearted sephiroth as the main villain of 6 and the insane Kefka as the main villian of 7.
I personally think it could work because Sephiroth's grimness would fit in nicely with 6 and Kefka would make a good opposite of Cloud (who'd be more serious and not an amnesiac in the remake).