What can we say about Counter-Strike: Source that hasn't been said before? It is simply the benchmark for team-based online shooters and, four years after its release, it's still one of the most popular game in its genre. In complete contrast to Enemy Territory: Quake Wars, it focuses on small environments and incredibly intensive small-scale battles with one-shot kills the order of the day. If you want to test all elements of your first person shooter skills in one go, this is the game to do it.
We test using the 32-bit version of the game using a custom timedemo taken during a game against bots on the cs_militia map. This has a large amount of foliage, so transparency antialiasing has a significant impact on image quality and performance, and is generally one of the most graphically intensive maps available. We find a framerate of at least 60fps is required for serious gaming as this game relies massively on quick, accurate reactions that simply can't be compromised by dropped frames.
All in-game settings are set to their maximum and we test with 0xAA 0xAF, 2xAA 4xAF, and 4xAA 8xAA. Transparency anti-aliasing is also manually turned on through the driver, though this is obviously only enabled when normal AA is being used in-game.
All the cards on test here rattle through this game with consummate ease so there's little to choose between them. At the maximum settings we tested at, though, the HD 4850, HD 4870 and nVidia GTX 260 all pull away from the crowd. So if you want to game at 1,920 x 1,200 or higher any one of these three cards will be the way to go.