Warum? Das ist so.

durch den anderen Speicher, hat die Xbox 360 meistens die Möglichkeit 2xAA zu nutzen.
Je nach Spiel haben auch PS3 Spiele AA...
Nur um einpaar zu nennen:
Heavenly Sword = 1280x720 (4xAA)
Burnout: Paradise = 1280x720 (2xAA)
Call of Duty 3 (screenshot) ~1088x624 (2xAA)
Call of Duty: Modern Warfare = 1024x600 (2xAA)
Call of Duty: Modern Warfare 2 = 1024x600 (2xAA)
Call of Duty: World at War = 1024x600 (2x AA)
Full Auto 2 (demo) = 1920x1080 (4x AA)
GT5 Prologue (demo) = 1080p mode is 1280x1080 (2xAA) in-game while the garage/pit/showrooms are 1920x1080 with no AA. 720p mode is 1280x720 (4xAA)
Haze (demo) = 1024x576 (2xAA)
Metal Gear Solid 4: Guns of the Patriot = 1024x768 (2xAA, temporal)
NHL '09 = 1280x720 (4xAA)
Pro Evolution Soccer 2010 = 1280x720 (2xAA in-game, no AA cut-scenes)
Tom Clancy's EndWar = 1280x720 (2xAA)
Tom Clancy's Rainbow Six Vegas 2 = 1280x720 (2xAA)
Uncharted: Drake's Fortune = 1280x720 (2xAA)
Uncharted 2 = 1280x720 (2xAA)
Viking: Battle for Asgard = 960x720 (2xAA) - AA buffers are merged to a 1920x720 framebuffer, which is then downscaled to 1280x720
Virtua Tennis 3 = 1920x1080 (2x AA)
List of Rendering Resolutions + basics on hardware scaling, MSAA, framebuffers - Beyond3D Forum