Doom 3: Why is Radeon X800 Series behind GeForce6?
 

For the moment, the good performance of the GeForce 6800 series does not seem to fit into the usual picture: Everywhere, where modern engines are used, the Radeon 9800 /Pro/XT display adapters performed much better than the GeForceFX 5900/5950 display adapters. The new generation (X800 vs. 6800) provides a more balanced image, the GeForce 6800 series can bring into play its strength in some games but without delimitating clearly from others. In case of other games it is final that peak performances comes from ATI. Doom 3 now is the "runaway" from this well known picture.

http://www.3dcenter.org/artikel/2004/07-30_english.php