In the gaming world, A company will make a game for the sytem with the highest User base, and then port it to the other systems. The Wii does not count in this situation, as it's specs are way too low to have Wii ports on the PS3 or 360.
Last generation, the PS2, while not being as powerful as the Xbox or Gamecube, had the highest user base, so games were made for that system, and ported over to the xbox and gamecube.
This generation, games are being made for the 360, and being ported to the PS3. But with all of the problems developers have with programming for the PS3, the games do not end up as good as they are on the 360.
Lee, you mention 3 games that you play all day for the PS3, one is a launch title, a mediocre one at that, and the other two are multi platform. For every single PS3 exclusive game you can name, I can name 2 or 3 360 exclusive games that are better than it.
Resistance - Gears of War, Halo 3, BioShock
Motorstorm - Forza Motorsport 2, Project Gotham Racing 3, Project Gotham Racing 4
Lair - Any 360 game, lair is fucking terrible.
Final Fantasy - Mass Effect, Eternal Sonata
It really amuses me how butthurt people get over this.