FPS alone is a useless measure. A film @ 30FPS will not look the same as a game @30FPS, simply because the timing between frames in a game is not consistent (unless vsync is done at that FPS), which makes the biggest difference. For a real measure, you should actually measure the longest time between frames in an interval.
I had a crossfire setup, which reported 54 FPS, but it looked pretty much exactly like one card @ 30FPS, and the reason is that the one frame would come out after 30ms, then one after 7ms then the next after 30ms etc. Which made matters worse, is that those frames weren't computed based on those intervals.
That said, once you have gamed at 60+FPS, nothing else will ever suffice.