I figured out what decides a game’s sales.

[theRepublic]

supermario128 said:
Only kids and people who know nothing about games will buy them based on the cover.

Which is a lot more people than you realize.  Only a small portion of gamers actually spend their time talking about video games on the internet.

Every time I walk by the video game section of a store, there are always two or three people just starring at the games.  A couple of weeks ago there was a kid going through the whole shelf, pointing at a game and saying "yes" or "no" based solely on the covers.

Games that look cool sell well.  Not really a big surprise.