The better test is 360/PS3 simultaneous releases where neither version is horridly botched (Fallout 3 for instance). In NA centric games (FPS games for instance) the 360 seems to do better, in Europe and/or Japan centric games (Pro Evolution Soccer for instance, or JRPGs when they start getting dual releases) the PS3 version wins pretty handily.
I would bet this will only pick up as the install bases get towards parity and the 360 gets hacked by pirates more and more often (its still kind of niche, but if games keep getting pirated well before release Gears style, it will be a much bigger problem).
When every game gets trophies that should help the PS3 version of games even more since it eliminates achievements as a reason to prefer the 360 version. That was a very smart move by Sony, now they just need to make sure all games support it 2009 and on.
Incidentally even a lot of America centered games end up higher in Europe and will certainly be higher in Japan. GTA4 for instance has higher weekly sales on PS3 now, largely from European demand. Add to that the Euro being worth far more then the dollar and a 500k advantage in Europe is worth more in terms of margin then a 1 million advantage in North America (since the Euro is worth 1.5 dollars a lot of the time these days). Again thats why EA earns most of its money on the PS3 now even though sales are still slightly higher overall on the 360.
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