actually if anything, Nvidia's 6800 should have better graphics with Smartshader 3.0
the 6800's performed better in benchmarks, but it has been disputed that benchmarks differ from actual use of the video card in gaming, a lot of people with X800's actually say that they get better framerates than those with 6800 ultra's actually playing games - although I don't really know for sure which one performs better, despite the benchmarks which show the 6800's ahead; like I said, benchmarks ususally differ from actual gameplay.
if you have an X800: you have an excellent card which is roughly twice as good as the 9800's
if you have a Geforce 6800: you also have an excellent card, which performs roughly twice as good as the 9800's
although if you have a 9800: you are still ahead of the gaming industry, no game has yet been made that the 9800 can't cut through
if one card is getting great performance in a great game, who cares if another card puts out twice the framerate? would you actually notice a difference if you're already getting hundreds of fps with a 9800?