the question wasnt whether you would go see it or not, it was who would play Geraci. If you didnt enjoy the book, feel free to quit posting on the topic.

Geraci - Vince Vaughn
Sandra Corleone - Monica Bellucci
Francesca Corleone - Natalie Portman
Billy Van Arsdale - Leonardo DiCaprio
President Shea - John Cusack

if there was a movie to be made, i would somehow revolve it around Geraci and use Sandra, Francesca, Billy as major pieces, along with President Shea and AG Shea.

for the smaller parts that would need to include Michael Corleone, I would probably use Jason Gedrick. most of the Michael Corleone parts in my movie would be implied or he would be spoken of. Or another good way to integrate him would be to have him be the narrarator (even use Pacino as the narrarator) of the movie and tell what is going on around him.