Half-Life. Or any FPS or 3rd person game with a trainer really.
Guys don't seem to realize, most girls aren't really that different from us, particularly in the sense that they don't want to look dumb playing a game. If a person ever likes action movies, they probably would enjoy a FPS; the question is, will they become too frustrated by learning the controls and how to play?
True story: My at the time girlfriend (now wife) got irritated at me for staying up too late playing Half-Life and Unreal. But I noticed that she would watch me while I was playing, clearly interested. So I showed her the trainer in HL, and had her set the game to 'Easy' and left her alone. {That's a big deal, really. Put her on the computer and then leave the room. Otherwise it is quite likely that they'll get 'performance anxiety')
Now, she is a kick-ass gamer. As I type this, she's in Ulduar with her guild in WoW, getting server-first bosskills. Not even fucking joking about that.
Speaking of which... If you think a MMORPGuh is more her speed, I can only provide this advice: Level with her, don't powerlevel her. Let HER control the pace you move at, and what you do. Nothing says "hamster on a wheel" more than being dragged around by somebody else. Yes, you can make suggestions based upon your experience, but remember that the sense of wonder that will really get her engaged and invested in the game will only result from the sense of personal discovery. If you try to do the 'guided tour' of Azeroth (or whichever one you choose), you're going to leech that out of the experience.
