Christmas Day 2001 saw the release of a full-on Hollywood biopic of the "Greatest of All Time," simply titled 'Ali.' Directed by Michael Mann and starring Will Smith, it didn't stray far from the sports biopic formula but it was executed to near-perfection.
Whether your screenplay is written in three or five acts, an audience can only truly appreciate a complete story, so I say why not implement a proven form that has satisfied audiences for over two thousand years.