In terms of skill with videogames, females as a group are most definitely inferior to males as a group. This, however, has nothing to do with the individual girl being incapable of being as good as a guy at videogames, it has everything to do with the fact that the demographic of those who play videogames regularly as a part of their life is highly skewed toward male.

I consider myself to be very skilled in Mario Kart DS, but my girlfriend bests me 2/3 times. That's because she actually cares about the game, she's played it as much or more than I have and she is passionate about being skilled at it. It's hard for girls to be passionate about being skilled at unappealing games that are clearly geared toward male interest and mentality, which most competitive games are: First-person-shooters, real-time-strategy, etc.

Girls on an individual level can in no way be considered inferior gamers, and if the Wii actually does what it's setting out to do, this will be a lot more obvious soon.