This is a really interesting question. Lately I've been playing a lot of games in the same space as my wife, and I've learned a few things.
Unsurprisingly, cinematic games can be enjoyed by bystanders. Uncharted 2, for example, was a big hit. It doesn't hurt having a globe-trotting Indiana Jones-esque storyline and some well developed female characters either.
Bastion, conversely, was a swing and a miss. Although I enjoyed playing it, she was bored to tears. It might have been the isometric view, or the cryptic storyline, or maybe the repetitive action, but it didn't work.
Darksiders was actually her favorite. The story was interesting to her; the crumbling, post-apocalyptic world was engaging; and she experienced the challenge of the game vicariously through me.
So this is my theory: go with a third-person action or action-adventure game with a good story, good art direction, and good music.










