I think in the US (probably true for Europe, too), a lot of people bought 360s for current games, when people bought PS3s for future games.
Maybe there are a lot more impulsive, I want it now people in the US. I don't think this is really a bad thing. People are buying the product which is satisfying them.
You could go on and on about how great Gears was when it was released, but a PS3 gamer was content talking about how great MGS4 was going to be.