I vastly prefer single player games. I'm most fond of RPG's and it is a compelling narrative that draws me into a game. I want well-developed, believable characters. I want to be the protagonist that the story centers on. I want to be the big hero that shapes the world around him. That isn't really something that can be done well with multiplayer games. I have no interest in playing games against nameless 14 year olds who practice 21 hours a day. Give me Dragon Age or Mass Effect any day of the week.