Oh please don't post any You Tube video comparisons. They are useless.
And LOOOOOL to the people who think Halo 3 looks bad. It has unbelievable light effects (talking about High-Dynamic Range Rendering)
Two of my favourite pics:
http://www.supercheats.com/xbox360/guides/halo3/wallpapers/halo3-wallpaper05-1024x768.jpg
http://xbox360media.ign.com/xbox360/image/article/803/803187/halo-3-20070711001714637.jpg