^this. I don't know how many times we have to reiterate the same thing again and again....
Generalizing the population of one subset of consumers to a related, but different other subset, without hard facts to support that generalization, is a fallacy of debate...a logic flaw that may support your argument, but honestly makes it no stronger.
IF the top 10 games for the 360 were 90% shooters and 20% shooters for the PS3, maybe you'd have an argument. A 60%-50% split is hardly definitive evidence though, particularly as Killzone 2 will probably be a top 10 PS3 game soon enough.
In fact, a larger install base, by definition lends itself to more diversity, while the smaller one would tend to be more homegeneous, good reasons why the PS2 had such a diverse install base (and the original XBOX had such a "shooter" centric one).