Several of the games you get with the PS+ subscription have coop. Double Dragon, Scott Pilgrim, Ratchet & Clank, LittleBigPlanet 2, and now Dungeon Defenders. My wife is not a gamer by any definition of the word, and we are able to have fun with most of those games.
We also play LittleBigPlanet Karting together. I tried to get her into Awesomenauts but she didn't enjoy it.