My girlfriend and I did a form of co-op on dead space. We would take turns trying to figure out what to do next, I was showing the game to her, and she liked it. A lot and she was really good at it. Afterall she has played RE4, Silent Hill etc.
My wife likes to play Lego Star Wars and Lego Batman with me. Her own games are Kung Fu Panda and Kingdom Hearts.
Lego: "FIll in the Film/Comic Series" here Games Guild Wars Marvel Ultimate Alliance Justice League Heroes Basically any Adventure game with Coop.
Mario Kart Wii, my GF loves this game. Sad thing is, she almost nearly always looses when I play her (she always knows when I'm intentionaly doing less than my best somehow, maybe it's one of the female super-powers or something?), and she always tickle-attacks me whenever I beat her. Oh well, at least she doesn't bludgeon me with the wii wheel.
My girlfriend and I have a blast with most co-op shooters like GoW and the Halo series. That's actually why I get frustrated about so many games making co-op only available online. I think it's often the case like my own where the person you want to play co-op with is sitting right next to you.
I got my wife to play Feeding Frenzy 2 on the 360 and she really enjoyed it. We play most of the games e3nine listed, but she really enjoyed Donkey Konga 2 for the GC/Wii.
dokapon kingdom. my wife tends to like rpgs and we got this the other day. it was so awesome to change her head to a lump of poop.
My fiancee and I don't play to many games together. One game though that has brought us together is Guitar Hero World Tour. She loves it just as much as I do. It's awesome.
My Wife Loves racing games at the arcade. she's actually pretty good. I'm just a little better. I can't wait to teach her to drive for real. I gave up all my game systems. too much money. OH and I forgot Karaoke KARAOKE KARAOKE KARAOKE. The wife and her family loves it.
RockBand 2,She hates it when we play Painkiller and Visions.. Halo 3, Mortal Kombat Armageddon, Lego Batman.