For me, it depends on my attitude. If I feel like having fun, the game could be alomst anything, especially if it is one-screen multiplayer. If I am in a bad mood either the game has to be really good or really relaxing.
I think the reason why companies don't care is it is less risky to make a game, say about dragons, and then people will buy it because they want to pretend they have a pet dragon on the battle field. Or a movie license. Then most of the buyers are moderately happy with their purchase because the game did the job... they got to ride around on a dragon. I know I wanted a overhead-shooter with lots of Aliens, Alien Syndrome is doing the job for me.
Unlike movies or TV though, staying power and big releases don't just come from the theme or noteriety. The games that sell really really well tend to be good (except sports games, some just sell because of the sport).
In case any one cares about my opinion: Mario Galaxy, BioShock, and Haze are going to be "the" good games of the year for each system.
I would cite regulation, but I know you will simply ignore it.
