Age of Conan pretty much screams with ATi hardware. I don't know if it is an ATi branded game but it runs very well on their cards.
EDIT: WTF is the HD 4850 doing there?
This is what Xbit had to say about the HD 4770 vs GTX 250 (9800GTX)
"The Radeon HD 4770 leaves its market opponents, Radeon HD 4830 and GeForce 9800 GT, far behind, outperforming them by an average 14 and 17%, respectively. The average difference between the new card and the GeForce GTS 250 512MB is less than 1%"