I'm always looking for something to play together... (on the 360)

I've been searching for good COOP games to play with my friends for about two years now. 
I've never gotten into competitive multiplayer shooting... 'cause I prefer mouse and keyboard for those games. ;)

I think the first (and one of my favorites) is (obviuously) Geometry Wars 2
I can't even remember how much I played that with my friends... unfortunately my wife's not really into it.  

So I've been trying to get some games that are fun and exciting to play for me and my wife. 
We tried playing a couple of the Lego games, but we both got bored pretty quickly: 
 - the gameplay's very repititve... 
 - and my wife wasn't getting any of the pop culture references... so that wasn't a success. 
After that we tried the following:
Splosion Man
 we played that for a couple of levels... but at a certain point it just gets too demanding for my wife... (she's not a seasoned gamer like myself) 
Lara Craft (Guardion of Light)... great game... entertaining... good puzzles... not too hard for my wife... a rewarding experience. :)
Blur... now I only recently bought this... but I'm already loving it loads! (and so is my wife)... :)  
We also tried Death Spank, CastleCrashers and Fable (2)... but unfortunately my wife wasn't into that very much. 
I guess I'm really just looking for a certain type of Arcade games... any suggestions?