Video games, on the other hand, are IMO time wasters. If we're talking about video games here I agree with your girlfriend, they should not be a significant part of an adult's life. There is no compelling reason for an adult with responsibilities to set aside 50 hours to play the newest God of War or whatever, and it makes you seem selfish for spending so much time with them.
I realize you've decided to drop this line of discussion, but I felt I should make comment on it. Your presumption seems to be that video games are a solitary endeavor and that it's selfish to waste time on them when you could be spending time with your family. I would suggest that would be true, if you were to secret yourself away in some hidden basement chamber, bathed only in the glow of a tv's light, far from those you love. My experience is actually the opposite of that.
My son and I play video games TOGETHER. A cooperative game of Halo: Reach Firefight, for example. Letting my son my find Golden Eggs in Angry Birds, for another. My daughter and I play Raving Rabbids together and we all play Guilty Party as a family. My wife plays few video games...she prefers RPGs and puzzle games (though in her youth she played Doom, Rise of the Triad and so forth). Having said that, she HELPS ME play games.
When I was playing Red Dead Redemption, she'd check on locations of items or quests. When playing Darksiders, she would help me with some of the puzzles, at which she is much better at solving than I am. When playing Assassin's Creed 2, she would pull up an interactive map at the laptop and help me hunt down items or tell me what I'd need to do to earn an achievement. When playing many games, my wife and son make me promise not to fight a boss or finish a story sequence unless they're there to see the battle/cut-scene/etc.
So even a single-player game is a social experience in my house. Multiplayer games? There are many and they see use. Whether it's Mario Kart with relatives, Soul Calibur IV with friends when they come over, Carcasonne with the wife on the couch, split-screen racing games or four-player Horde Mode in Gears of War 2...video games can be a profoundly social experience.
Just last Saturday, my entire gaming group got together...with our kids AND our spouses/girlfriends. And we ROCKED OUT to Rock Band 3, switching in and out of positions while getting food, singing along and enjoying the party atmosphere. Video games a selfish, solitary experience? I'm sorry that's how you view them. Luckily, that hasn't been my experience (or the experience of many).