Wasn't Godfather actually grounded in reality? I remember the wikipedia article on the book said there was a scene they couldn't include because it was too graphic.
Yes, the Corleones were based on the Bonanno family while their rivals the Brazzini were based on the Genovese family
A lot of mobsters took on Don Vito's manner of speaking after the movie premiered. Some mobsters cried during the movie apparently because they thought it captured la cosa nostra so well lol