I though of another way to appeal specifically to women: a game where most or all of the characters are female, and the male characters are irrelevant or nonexistent. The female characters would have to be well-developed, realistic, and not sexualized. I think this idea has potential, but it would probably require an all female dev team.
I had a dream last night that you had developed a game in which the main character was female. She was on a bicycle, cycling around in the dark, and it was really foggy, and she was humming some music to herself (what she was listening to on her mp3 player I guess). And loads of other details I think. And I thought: "gosh! that's really impressive. Anna did have a point here about women having the edge when it comes to doing female characters".