In quake use "timedemo" to get an average FPS.
in the console type "/timedemo 1" then run a demo and check the console for the avg. FPS.
Some demos are harder on the hardware the others, if you run the standard "DEMO001" or "DEMO002" you would get a higher FPS then if you run any of the intense test-demos that can be found on the web.
"/cg_drawfps 1" will show you the FPS during the game, but it changes all the time, and depends a lot on how many players, items, lighteffects ands so on that are visible.