Both the wife and I game. I get to play my MMO's and she plays her puzzle games and we both have fun with the latest Tomb Raider or GTA game out. The key for us was that we decided that if the other need "alone" time to game they got it. The other side of the bargain was making sure we also spent time together on the PS3 or whatever else struck our fancy.
Part of a couple that plays MMOs together as well. Admittedly, it took a bit of convincing to get the significant other to play STO (Not as much of a Trekkie as I am). I've known people that have experienced significant amounts of difficulty with managing MMO and real life time, which seems to be a pretty good cause of friction in relationships. But, I think that it's not a situation unique to online gaming and just about any hobby could be inserted in its place.