Splinter Cell: Chaos Theory
Splinter Cell: Chaos Theory, run with high-quality shadows and parallax mapping, hits the cards the hardest. As expected, the GeForce 6600 GT 128MB card is around 25% faster at the lower resolutions, and a smaller framebuffer doesn't count against it at 1600x1200.
The framerate situation only gets worse as we add-in 2x FSAA and 4x AF.