Okay, lets say an average looking guy in your eyes was standing next to an extremely attractive girl. Would he look just as average as before, less attractive or more? and the same goes for if he was to stand next to a hideous looking girl.
No. I'd be less intrigued to get to know him. I'd rather talk to an "average" guy alone, not with some strikingly beautiful girl. :) And if he was beside a hideous girl, I don't think it would make a difference to me. I'd still walk over and talk to him, but I'd talk to her too.