I am not into the whole online multiplayer at all but do love a good campaign co-op experience that my wife and I can play together.
Our favorites are:
Resident Evil 5
Dead Space 3
Resident Evil 6
Really wish there were more co-op games that focused on the campaign. The 8th gen, in particular, seems to lack many. If anybody know of more titles, please let me know. We have had borderlands on our radar and will probably try that.