Quake2 requires some minor setup to get it going. First, in the Quake2
directory, the install creates a symlink called libGL.so that points
at libMesaGL.so. This symlink should be removed or renamed. Then,
to run Quake2 in OpenGL mode, you would type: 'quake2 +set vid_ref glx
+set gl_driver libGL.so'. Quake2 does not seem to support any kind of
full-screen mode, but you can run your X server at whatever resolution
Quake2 runs at to emulate full-screen mode.