Most Helpful Girl
I think in the generation that is typically on GAG (18-29, typically) guys and girls cheat evenly. In older couples like in their forties and such, the man is more likely to stray.
Regardless of statistics, it doesn't make cheating by any gender less wrong. I think people typically blame neglect for cheating (guys usually blame sexual neglect while girls usually blame emotional neglect). Why they seek someone else out rather than solving the problem I don't have a clue, but cheating is wrong no matter how neglected the cheater feels.