Why do people never compare John Williams' works to that of Clical Composers?

It is my belief that John Williams is a genius in the genre of clical music. While some might disagree that his works belong in with the works of Mozart, Bach, and Beethoven, I think that it is simply a bias against composers who aren't dead or who live in the same time era as us. We look back and say, "Wow, that guy was a genius!" But I think we have a hard time looking next to us and saying, "This guy is a genius!" Agree/Disagree- Explain.