I think the answer to that is both yes and no. I mean, you rarely see supermodels dating super obese uggos unless the uggos have money or you are watching primetime television.
I think someone might be attracted to their opposite if they have really low self-esteem and hate themselves so much that dating anyone that resembled them in any way was a repulsive idea. I also think someone might be attracted to an "opposite" if they came from a household that restricted the idea of dating someone of a different race, ethnicity or value system.
Most people, in my opinion, strive to date someone that inhibits the qualities that they themselves cherish, while also having those that they would like to have or that confuse and excite them. Or, maybe someone has dated people like them for so long that perhaps they feel the need to date someone completely different. On some primal level, perhaps, we are attracted to our opposites because we would like our relationships to be completely devoid of emotional or intellectual "communication," and would instead just like to jump their bones. Sorry editing staff, I mean have sex with.
Personally, I am a little narcissistic. My boyfriend and I are almost completely the same, except for our body parts, which is nice because I am very heterosexual. On that note, heterosexuals have dated opposites since the dawn of sex. It is arguable that men and women will never understand each other because we are so different.
Being completely honest, if the need to procreate didn’t exist, we probably would have killed each other by now. So yes, we must be attracted to our opposites. I would like to believe, though, that we are attracted to someone who compliments us and is only different in good ways, ways that help strengthen the relationship.