Army of 2 was fun for a while, I'd recommend it as a rental for a weekend or something. Resistance was awesome for coop game play. I personally enjoyed Kain & Lynch, although I'm sure it's not for everyone. Rock Band, if you haven't played it before it's a lot of fun even though the instruments are pretty steep cash wise it has great replayability. Especially with friends and family. Lego Star Wars is pretty fun, and some parts made me laugh (more or less a chuckle, quietly kept to myself). I know you said FPS games aren't your genre of choice, but most of the good coop games out there are FPS. Sacred 2 is your best bet for good coop action that'll keep you coming back for more. **** has a new MMO coming out as well, if you haven't read any articles about it just search "The Agency".
Btw, all the games I listed apart from, The Agency, are split screen games. Or can be played with people offline.