"Nobody says Mozart's first few works were brilliant. It wasn't until he practiced for years that he became a virtuoso."

Are you trying to be ironic? Mozart's first work was http://en.wikipedia.org/wiki/Andante_in_C_for_Keyboard_%28Mo..., written when he was 5 years old.

Mozart's the canonical example of somebody who didn't have to practice for years. Obviously he did spend thousands of hours practising as he grew up, but that's a nuanced argument. You'd be much better choosing pretty much anybody else for your example.