Quake III
An easy benchmark for all concerned. Some may question its validity in an age with vertex and pixel shaders v2.0, but it's still heavily played and boasts an engine that's been licensed by many games companies.
Nearing 300FPS with 4x AA and 8x AF shows what the Tyan G9800 PRO-M thinks of this benchmark.
1600x1200x32 almost doubles the pixels over and above 1024x768x32. That's why we see just over a 50% performance drop from most cards.