I disagree with your analogies. Good games tend to do well. The catch is a truly good game is not an easy endeavor. But if you can pull it off, generally you can reap rewards from it. Gamers tend to be pretty educated on their hobby, especially if you compare them to your average music cd or dvd shopper. And gamers always have room for another game if it's good (just ask any gamer about their "backlog", a completely ubiquitous concept in the hobby). Most people have no need for more than one social network. I've challenged myself to find a truly excellent iOS game that didn't sell well, and despite a lot of digging, I have yet to find one.