Urgh, I have the annoying compelling need to reply to this thred and dump my thoughts on the subject. Normally I just ignore this kinda stuff and think, who cares if girls are into games or not.
(Complete brain dump warning - little structure to this post)
Anyhoo...
Essentially I think people are looking at it wrong. We seem to be saying why aren't girls playing games? The answer is that most games are targeted at the 'core gamer' i.e. the men, so basically there just aren't enough games for girls. We seem to use this question in a way that assumes we want girls to play the kind of games guys play, but if we look at film, books tv etc we can see this shouldn't be the case. In the other entertainment industries there are things aimed speciffically for women and others specifically for men. For example desperate housewives, ugly betty, romatic comedies (bridget jones etc) these are aimed at girls (Note I say aimed - it doesn't mean there aren't some guys that like them). And obviously therefore there are tv programmes and films (I guess horror and action mainly) aimed at guys (but noting there are girls that like these).
Fortunately we are now seeing games aimed at girls like sims, cooking mamma or whatever. And this is a good thing as it will get consoles into the hands of the type of girls that wouldn't normally play games and then maybe they can explore more games that are for both genders.
Party games also seem to be a good way to get girls into games. I think the main issue is that girls are more likely to want to spend time in a social setting then guys. THey like to talk and do things together. I know alot of girls that have bought playstations purely for DDR and singstar.
In terms of social conditioning, yep it's probably true that most aged 20+ girls grew up with games being a boys toy, but now it is much more acceptable for little girls to have a DS (usually pink ones :] ) So this in the future will lead to girls being more used to having games about as a form of entertainment as much as any other. I have a niece who owns a ds, a whole bunch of girls games and games like mario etc and her and her friends are allways playing them. So the future of girls and games is there I think, a revolution is starting! ha ha. Also at the other end of the spectrum my Grandma has a DS and thouroughly enjoyed playing the wii at christmas.
So generally I think we are in the time where girls are being introduced to games (mainly thanks to nintendo) and we will see a change in this problem(if you think it is one) in the next 10yrs or so.
In response to the original post I think if you want to get girls to play games, get a wii, get some party games, get some alcohol, invite them round and play for fun. If they like it it could become a regular thing.
Also in response to some other posts, not all girl games are wierd, not all girls think about shoes all day and some girls do just like games and aren't in it because they want to be different! Also there are girls who like to play GTA, FPSs and torture their sims!