quake 2 rendering comparison
Here's the same scene, rendered with the software engine, and then again with the hardware (openGL) engine (with a Riva TNT card).  Some differences: the hardware engine has colored lighting, while the software has only white lighting. The hardware engine also has texture smoothing.
software:
hardware:
(the hardware image was shrunk from 800x600 to 640x480. Note that the hardware running at the higher resolution is still much faster than the software running at the lower resolution.)