Musical complexity in clical music?

I hear clical music purists going on about how "superior" clical music is to other kinds of music due to complexity. Not all of it seemed to be that complicated. Beethoven's fur elise seemed to be a fairly simple tune, and yet it's considered some of the best clical music ever created. If you ask me, fur elise isn't any more complex than some of the most complicated rock, pop, rap etc. music that has come out in the 20th century. Anyone care to disagree?