I think to begin with, you need that initial attraction. It's that first bit of chemistry that instigates the dating/relationship.
However, as a relationship develops and your feelings for that person grow, their appearance is the least important aspect. You start looking at them differently, as if any faults they might have don't matter in the slightest. It's hard to explain.
I can't stand people that base their preferences entirely on looks, its so superficial. Sure, you need to be attracted to someone sexually, but I seriously have friends who will not date someone because they don't like the formation of their teeth, or their eye color.
At the end of the day, nobody's going to be beautiful forever.
