EDIT: Woops! I completely glazed over the general question of the most attractive character! (NOT females vs. males). I'll stick by my choice though (:
I sure had a lot of trouble with this one. The thing about anime is that they make every character very physically appealing. It's the personality that will define one as the most attractive. I wouldn't be able to choose one!
So through all that thought, I chose the female character from Interstella 5555. They don't give her name, but if you pay attention, they do give a profile. (the two are the same person)