Well that entirely depends on what is your definition of finding a game enjoyable, I don't find a game running at 20-30fps max by no means enjoyable.
A 2400 or 8500 can run most games at 1024x768 at far greater FPS than 20 to 30, especially if you lower a setting here or there.
It's higher resolutions and next-gen titles that will cripple them. Guild wars at 1200x1000 might be iffy, but guild wars is a pretty easy title to run, and it's not an FPS. Might even handle it.