Wait... Why did you only include exclusives on PS3 side... Yet used multiplatform game for the 360 side? Gears of war is multiplat you know...
Sales =/= quality
If GT5 were out, it would sell more then Halo 3. Anyone who sees that as a ridiculous statement, look up other GT sales. In fact look up GT5P, a demo which sold 3 million copies. A DEMO. They only released the demo to get funding for the game, so they could do things like buy cars, crash them, to see real effects of a crash. They are buying 500 thousand dollar cars, and crashing them. GT3 sold 14 million. GT4 sold 9.6 million. GT1 10.6 million. They all sold around the same. If you think demo sales effects final sales, look at GT4p, it sold 1.5 million, and main game went on to sell 10 million.
It's in a new league. PS never sold FPS games before. It sold RPGs, and racing, and fighters. Xbox always sold FPS games, moving a little into WRPG territory. That is a fact. Look at JRPGs, released on 360, 200-500k LTD(One exception being Lost Odyssey), released on PS3? 220k first week in Japan alone, while 360 has worldwide sales at around 150k first week. It's sad really, releasing a JRPG on 360 is suicide, I do not understand publishers doing that, it has to be microsoft paying development costs.