I agree with Petitebrunette too! If a guy is significantly less attractive than I am, I feel like I'm not good enough to get someone more attractive. (yes I know it's shallow). If the guy is like a model I'm pretty sure it would get tiring having so many other girls like him, although lots of girls like my current boyfriend too, so I guess it's not that big of a deal. It'd be a problem if he was super flirty because he knew he was hot, but less attractive guys can be flirty too.
I'd say my boyfriend and I are both pretty attractive, and around the same level. I mean some perfect guys might be more handsome/hot, but I'm not any more attracted to them than to my boyfriend. And those kinda guys are usually not found in real life, just movies haha.