I've heared that girls actually got slightly better reflexes than guys (no big difference, but it's still there). And in that case, girls would actually have a slightly higher potentional than guys when it comes to gaming. It's just that they never (or very rarely) bother to get as good at games as the extreme hardcore-playing guys.

Random cool fact: One of the better Samus players in the world in SSBM is actually a girl. She's not THE best Samus player, but I think it's pretty safe to say she's atleast one of the best.