... AFAIK there is no such thing ... That's why Apple does CPU spec benchmarking and also all those Photoshop actions & real-life comparisons...
However, people often use games to compare hardware, if details don't matter much... like the FPS (Frames per second) in Quake III. You can also look how fast (with a stopwatch) your computers can do something in Photoshop or another program...
If there would be benchmarking app like you want, there would be a lot less discussions between mac freaks and PC heads on who's got the fastest machine ...