Actually, I rather liked Aerith. I don't think she was anywhere near as 'pure' as a lot of people tend to think she is. In fact, to be honest, I think she was a little crazy. Think about it: she grew up in the slums, more or less, hearing the voices of the Planet, and yet she still seems not to be negatively impacted. Then, on top of that, not very long after she feels her old boyfriend (who, depending on your interpretation, she might have actually loved rather a lot) enter the Lifestream, this guy who copies him shows up.

Yeah. If she's normal, Rufus likes kittens.

But I already mentioned that my vote was for Tifa. I don't hate Tifa or anything, but she's far from my favorite character in the game. She's really very overrated, and I'm not sure how much sense her sudden change of heart as regards Cloud makes. It seemed like she didn't even like Cloud for himself, until he half-became someone else. Sure, she stuck by him after that, but I don't see the arguments that she had this great pure amazing love for Cloud. She certainly didn't like him when they were kids; in fact, in the 'promise', it seemed to me that she was just using him so that she could experience being rescued. Then, while she's very tough physically, she doesn't really seem to have much emotional fortitude. To be fair, I think she improves, but the whole combination is still enough to make her not my favorite character of the game.

As for my favorite, well. That would take some thought to pick.