The 1999 first-person shooter Quake III runs at 1280x1024 on the Pi without a hitch to the frame rate, thanks to the computer's relatively powerful graphics processing unit (GPU).
The Pi graphics capabilities equal that of a first-generation Xbox. But don't expect the latest games to be available on the Pi. The only reason Quake III was able to be converted is that its code is freely available online.
The Pi's GPU is capable of processing 1Gpixel per second and 1.5Gtexel per second, and can carry out 24 gigaflops.