If everything we say is pure opinion how can you say we're totally wrong? I'd argue that the people who keep buying all the big games on the system have very limited taste in games being how similar they all seem.
Out of the two lists in the gamefaqs page you linked us to under top 10 games, 6/10 of the games are shooting, and that's not even counting the games that just get on there before they're out right now and people are familiar with the property, like as far as I've seen, Afro Samurai isn't some big hit game, so we can kind of argue that the rest are real big games, that's still 6/9 games with significant shooting.
Then on the top 10 message board listings there you have another 6/10 with tons of shooting (I say it like that because while GTA4 and RE5 aren't shooters, they still have a significant bunch of shooting). That brings me to another point, look at RE5. Resident Evil is supposed to be survival horror, now it just seems like a co-op zombie shooter. Everything's moving to shooters. Fallout 3 is often called Oblivion with guns. That's just the nature of the system. What are some of the biggest games on the system? Halo 3...shooter, Gears of War...shooter, one of the most critically acclaimed games on the system, Bioshock...shooter.
Meanwhile, also on gamefaqs, look at the top 10 Wii games. 1 fighting game, 2 simulation games, 1 racing game, 1 adventure game, 1 RPG, 1 action game, 1 shooter, 1 music game, and 1 strategy game. Little more variety there.
Also, it seems that if a game's not a shooter on 360, it has to have a certain amount of violence in it to be considered "mature" and desirable for people to play. It's just tiring. I've never liked violent games, especially when they all act the same, which is why I can't find much I want on 360.