I was a little taken aback by that post your cousin made too, actually, but I thought 'eh'. I am considered good looking by some, and my husband, well, not so good looking. I remember one of his mates commenting - wondering how 'such an ugly b**d' could get such a hot chick while the rest of them are still single. That attitude, I tell you is probably the reason why! The answer to the question: Guys that aren't as good looking have to make up for it in the personality department, and generally aren't such arrogant jerks as those who rely on their looks.
I think many of us can be shallow to some degree when it comes to choosing a partner - it's just where we draw the line. Sims 3 didn't take looks into account (even though sims 2 did) but they do care about money and personality clashes. Money and personailty is less controversial than being turned off, for example, by someone with different skin/hair/eyes etc. and probably a much safer route for EA to take than in sims 2.
