Initially looks are what attracts you to someone, but I'm talking VERY initally. As in, my boyfriend first spoke to me because he was attracted to how I look, but he first realised I was someone he wanted to be with when he quoted Terry Pratchett at me and I got the reference. So basically, since about the first half hour of us knowing each other, looks have been utterly irrelevant.
In my opinion and based on my experience, it is personality that makes and breaks a relationship. Appearance is for one-night-stands and shallow people. But of course that's just me and anyone's free to disagree...however, if another person says that being chubby is a reason not to fancy someone, I may have to find out where they live and sit on them until they're sorry!