Shooters are like meat and potatoes, they're easier to make and easier to sell, but they aren't the entire market. Of the top 10 best-selling video games of 2012 only 4 were shooters, 3 were sports games, one was a dance game, and two were action-adventure games (assassin's creed and lego batman). This doesn't count MMO subscriptions which would have put WoW into the top 10.