i think tifa and aeris are really pretty, especially in AC. tifa's gigantic chest is a little much, though.
however, i actually think tifa wins, hands down. aeris is beautiful, but.... MAN that woman wears a lot of pink! i liked her dress in KH, with the absence of her little red jacket. i like the little red jacket, but her dress looks better without it.
aeris looks way better in KH2. she's not so pink.