What wasn't revealed in the movie was that Michael had the plans for the Flux Capacitor. That was going to be his trump card if he couldn't kill all his enemies....again.
Just think:
He could have stopped the hits on his father and Sonny and then gone on to be a math professor....this proves he never really wanted to be legitimate.
He could have saved Appolonia which proved he did love Kate all along.
He could have reversed the order to kill Fredo which proves he never really regretted the decision.
Most important, he could have had someone looking out to see wh opened the drapes. This would have saved all that trouble of traveling to Cuba.
