there isnt one. different programs test different things. prime95 does a good mix, but no video.
the different tests are designed for different users and to test specific parts. thats much more useful than 1 single test. that way, you can know what you have to spend money on to make your computer better
if everything was mixed together, and you got a score of 30000 for the all around benching program, you wouldnt know your strengths or weaknesses.