Tom Clancy's H.A.W.X. should be the game where AMD's Radeon series should really shine, but unfortunately Nvidia did tweak its driver for this game, which means that HD 5830 still just trails the GTX 275, as in most of the benchmarks.
Crysis is still a most favorite game benchmark although it is already a quite old game, but when you see that a top notch HD 5870 barely reaches playable framerate you can see why this game is such a good benchmark. The HD 5830 will get you up to 1920x1200 resolution with 4xAA but at 2560x1600 with the same settings it still falls below the, what we like to call, playable framerate.
Far Cry 2
Far Cry 2 is the same story as with most of the game benchmarks, ATI's HD 5830 is somewhat slower than the HD 5850 and trails the GTX 275 quite well.