Seriously, I believe that there is material for a such a feat. No easy feat though. Very challenging as it would require great amount of talent, ideas and will into creating a satisfying motion picture which doesn't subcumb to today's moviemaking, but has real quality put before and front of the cameras.

The parallel story I don't think it will work because it would like beating a dead horse. Vincent is in no way TOO similar to Sonny, as he rose to be the head of the family AFTER he morphed from a single minded to a open-multidimensional minded character, something needed for the place of a Don Corleone.

So a prequel and a sequel, handled well, could fare well. The prequel to the original Godfather would be mainly about the Maranzzano (spell?) wars, and Vito's try to bring peace in the crime world, with occasional appearences from Moe Gren and Hyman Roth and Don Altobello. All of these from the book and the stuff Puzo wrote in his THE GODFATHER PART IV script. Sean Pean would Vito Corleone, the rest can be figured out, and at a special small appearence, Robert De Niro as Al Capone, reacting to Don Vito's letter after Luca would kill Capone's two men (thought it could be fun to bring De Niro play Capone again to tie THE UNTOUCHABLES to the Godfather universe, and see De Niro as another character after playing Vito in PART II ). The sequel would alla about Vincent Mancini and his extension of power as he deals with international mafia families, from Russia to Columbia and stuff, you get what I mean. Frank Hagen, after returning from Engald where he studied Law practice, would be the consiglieri and would share a great friendship with Vincent. Etc. etc. pretty much what EnzoBaker wrote in his script. In the end, though, Corleone House would dramatically fall and every Corleone-related would be killed, except for Vincent (or his son, I don't know), who would return to Sicily, poor and penniless, with only one legacy left to him - a small farm near Palermo, and live under the name Antonio Andolini, restaring the family line that died when Don Ciccio killed the Andolini family and forced the young son to live elsewhere undert the name of his village. The year would be 2001. Exactly 100 years since Antonio Andolini died.

What do you think?

P.S.: In any GODFATHER PART IV that includes Don Vito, I think Sean Pean is the best man for the role. De Niro is way to old now, and Pean with a little make-up could resemble both Brando's and De Niro's Vito Corleone not only physically, as actingly as well.