While Crysis was considered a brutal test for the past generation of GPUs, the torture test for the current generation is Metro 2033. With the eye candy turned up to the max, neither of the video cards are remotely playable. Especially for the FPS genre, framerates are too low to play save for small portions of the demo.
To make Metro 2033 playable on both the 6870 and GTX 560, the quality preset had to be changed from Very High to High, and the anti-aliasing method changed from MSAA to AAA. While you may note that the minimum framerate is a paltry 9-10fps, this is due to a weird artifact in the benchmark. Both of the video cards reported this low framerate for the 32nd frame, but the rest of the timedemo was smooth and mostly over 30fps (there was one occasion with both the 6870 and GTX 680 where the low was between 25-30fps, but it only lasted for a couple of seconds). The Radeon HD 6870 consistently took a small lead throughout our Metro 2033 tests.
DiRT 3 uses the EGO game engine, which was developed by Codemasters. Other than the DiRT series, it's also used by the popular F1 racing series games (also by Codemasters). It uses DirectX 11, and the same game engine will be used for the upcoming DiRT and F1 games due to be released late this year. Both the 6870 and GTX 560 are easily able to handle DiRT 3 with maxed out settings, with the minimum framerates achieved well above 30fps. The 6870 was faster though, and it beat the GTX 560 by 8%.