For boys, just being able to shoot something and have pretty explosions is kind of enough, and computers are good at that. Computers aren't good at the kinds of things girls like to do. For girls, it's not about a spatial universe, it's a social universe, and this requires much more sophisticated technology than is currently available to us. And the things she wants are like eight years off. She wants characters that will actually talk intelligently to you, and if you think of the kind of computing power and software innovation that requires, it's immense.
Girls are very demanding.
That it can be a very scary place when your best friend is trying to kill you. Doom made the Net a very compelling experience in a much more adrenaline-intensive way than chat rooms. When you're in a Doom death-match, there are people stalking you, monsters trying to kill you. You observe that the most common premise of video games today is a world in a state of anarchy. Anarchy resonates for many reasons.