To be honest, I think one of the only ways a game of this nature could be a success is if you played as a soldier or button in the Corleone family, possibly taking orders from the likes of Tessio, Clemenza, or Sonny. As you work your way up, certain parts of the film will play out, and you'll be able to take part in them. Like maybe the war the Tattaglia and Corleone families fought after the killing of Sollozzo and McKlusky. Remember, the game wouldn't have to exactly replicate the films, just intertwine with the existing story. If the developers went by this, the game could actually work.