My sister plays more games than anyone here, probably, excluding people who aren't in fulltime employment. It's extremely rare that she won't be sat in front of her PC, maybe 1 hour tops per day excluding sleeping/eating/work. If she's not playing at the weekend, 9 times out of 10 it's because she's gone to play 'real life' roleplaying games somewhere in the country. Anyway, as far as computer games go, it's definitely RPG (including oldfashioned MUDs) or Strategy games that she prefers - she's pretty hopeless as FPS.
Now, I'll probably offend some people here, but the fact is that it's a lot easier to get 'noticed' as a female gamer. By which I mean that top girl-gamers can start up their own clan, get their own sponsorship, compete in 'female-only' events and so forth. That's not a critisism of them, it's just a fact. Yet there for every girl who is able to be pro (or semi-pro) in gaming, there is probably 10 guys who are equally as skilled if not more so, but because of their gender, will never get those same opportunities.
Of course, the above sounds a bit like I'm saying "girls are rubbish at games", but that's not what I'm driving at. What I mean is that lets say you have a girl who is roughly the 100th best player in the world in a given game (assume it has a fairly big scene). She will get a lot of attention because she her gender opens doors for her that would otherwise be closed. Whereas a male player who is the around the 100th best player in the world, will likely have much more limited opportunities.
A top girl gamer (in most, not all games) will very rarely be able to compete with a top male gamer - this statement is proven by the fact that hardly any major money tournaments (excluding female-only, of course) are won by women. If you're a girl, you don't need to be one of the best players in the world - you simply need to be one of the best
female players in the world.
As for my gf, she doesn't play 'real' games, just stuff like solotaire, suduko and stuff like that. I don't think she approves of me still playing games at 26 and to be honest I feel a little embarrassed about it, so I've only done it once or twice when she's been around. Gonna be interesting when we buy a house together