I would have to say I hated a few different things.

The pacing was one, until you left Midgar the first time you were basically stuck in one long hall with only one way to go. Then you leave and you get that long flashback of Cloud's hometown and such. I suppose maybe the first time I played I was kinda interested, but now I just want a big skip button over that whole part.

Sephiroth didn't give me much of a villanious vibe as much as say Kefka did. Sure he was imposing and powerful but other then the flashback and watching him kill Aerith you have no real scope on how powerful he really is other then the game tells you that he is a badass so he is.