I think if they made a 4 it should be about stuff thats in the book that they didnt show you in the movie. Kinda like they explain how things happened and stuff. I think that would be awesome!!!
I'd personally rather have Young Vito/Sonny, and Luca etc.
I'd like to see more of Sonny and Luca, I feel Luca was killed off too quickly in GF1. They could of used him in plenty of scene's avenging Vito's hit. The book decribed him as a ruthless killer(even Vito was intimidated by him).
"He who fights with monsters should look at it that he himself does not become a monster... when you gaze long into the abyss the abyss also gazes into you..."