I dislike miniskirts, and Tifa's was pretty short. She showed a lot of skin, and that was just part of her design. She definitely isn't the worst of the worst though; as mentioned, her breasts aren't just spilling out over her tank top, and her miniskirt isn't basically a thong. And, unlike them, at that point she isn't that old. In AC, she doesn't show as much skin and ditches the miniskirt. It shows maturity, character development. Her CC outfit shows her wanting to impress Cloud, which could mean a variety of things. One could be insecurity with herself; another could be how she thinks Cloud thinks. There is my analysis on Tifa's clothing.
And, yeah, Aerith's dress is only buttoned halfway. In her concept art, anyway; does she wear it like that in AC and CC? I can't remember...For an FFVII remake, they'd have to be careful about it or change it, because wind (even during attacks) would...
However, weighting Tifa's physical appearance and clothing above her personality (combined with the fact that she does change her attire eventually) just shows a lack of debating skills. If love was based on such a thing, most video game characters would have no good lover. Not only that, but Cloud would come off as much more of a jerk; it's not like Tifa is sleeping around with every guy she sees.