And On An 30" (2560x1600)?
Could you play on a 30" with the two most powerful cards of the moment, the GeForce 8800 Ultra and the Radeon HD 3870 X2? Mostly the answer is yes, but not with every game (don't even think about playing Crysis) and you'd better forget antialiasing. But does the ranking change between the two cads in this resolution? To find an asnwer, we've tested using a Samsung 305T.
The situation still favors the HD 3870 X2, the averages (excluding Age of Empires 3 which is unplayable) only give it an 8.4% lead. The GeForce 8800 Ultra only beats it in Test Drive Unlimited. In all the other cases, the two cards are close or the HD 3870 X2 takes a clear lead (which happened in three games: Supreme Commander, Oblivion and Unreal Tournament 3).
This is a logical behavior however. In such resolutions, the cards are limited by their respective, yet similar, memory bandwidths and capacities.