That would have to be Beethoven, not because he was a great composer or the amount of work he completed in his lifetime. Its because he composed my favorite classic piece witch would be his Symphony #7 particularly the Allegretto. To me it is a very powerful and moving piece, not fancy and assuming like Vivaldi or "epic" like Wagner, this is just an amazing piece of music to me and Beethoven would have to be my favorite for that reason.