The Elder Scrolls IV: Oblivion
We turned up all of Oblivion's graphical settings to their highest quality levels for this test. The screen resolution was set to 1920x1200 resolution, with HDR lighting enabled. 16X anisotropic filtering was forced on via the cards' driver control panels. We tried enabling 4X antialiasing, as well, but got inconsistent results from Nvidia's current 158.18 drivers for Vista x86. Antialiasing only worked intermittently, and we haven't yet found a consistent work-around or fix. As a result, we've tested without AA.

We strolled around the outside of the Leyawin city wall, as show in the picture below, and recorded frame rates with FRAPS. This area has loads of vegetation, some reflective water, and some long view distances.

Grabbing a pair of GTSes will buy you more performance in Oblivion than the Ultra.

Rainbow Six: Vegas
This game is notable because it's the first game we've tested based on Unreal Engine 3. As with Oblivion, we tested with FRAPS. This time, I played through a 90-second portion of the "Dante's" map in the game's Terrorist Hunt mode, with all of the game's quality options cranked. The game engine isn't compatible with multisampled antialiasing, so we couldn't enable AA.

This Xbox 360 port will tax any current video card at this resolution, but the Ultra once again comes out ahead of the pack.