Tifa. Of the girls I've seen in the various games so far, I would say she comes across as the most interesting and genuine. It helps that she is attractive, it helps that she is in the first FF I played (and my favourite game of all time), it helps that she is shown next to Aeris, who I simply could never stand in that game. I guess overall, though, I just like how there is a lot left to the imagination - well, obviously not much in the looks department, but in her mind. She kind of reminded me of girls I was into at the time, too - shy but attractive girls who weren't interested in throwing themselves at the guys they think is cute (a la Aeris), but rather just relying a little more on romance and having dreams and all that.

I'm reading far too much into it, of course, but that's pretty much the only purpose of this thread, right? xD