There has been a flood of co-op games this year, and they've been really popular. People love to play with one another. Everything from Red Alert 3 to LittleBigPlanet shipped with some form of online co-op, people are eating up the co-op experience. And why shouldn't they? It's a whole heaping ton of fun. But of course, the biggest selling co-op experience this year has likely been Wrath of the Lich King.
Let's face it, Massively's beloved MMOs are pretty much the thesis of co-op gaming. Granted, you can solo in World of Warcraft if you like, but the core experience of that game is playing with other people -- be they friend, family or complete stranger.