Assuming the Bonanno family as a reference for the Corleones, since Joe such as Vito became bosses in their youth and tried to make his sons the new bosses of their families.

The Godfather begins with the wedding of the daughter of Don with a low level associate, while in reality the daughters of the bosses, especially if Sicilian, marrying on other sons of a mafia boss or a high-ranking mobster such as bill bonanno with Rosalie Profaci;

For no reason it would be allowed to a non-Italian to become a made men, much less a consigliere,the title was gave to old and trusted mafiosi, who had the task of settling the issues. In reality don corleone would adopt tom and would give his surname but wouldn't go further;

The killing of a police captain would have caused a sensation and would create serious damage to the corleones but there would have been no war between families and how strong were the corleone, couldn't fight against all the other families at the same time;

No bosses such as Michael, would have moved his base in las vegas that being open city was of no family in particular, since his power base was in new york;

Corleone family has at least 100 made men including at least 10 capos, while showing only Tessio, Clemenza, Al Neri and others in the new books of the series. Certainly Don Vito knew the two ever since as he was young and had more confidence but doesn't show any other capos;

The idea that a mob boss can't refuse a hearing on the day of the wedding of his daughter is a nonsense; the mob boss have always done what they wanted;

Michael wants to rebel against his family and for this bride Kay and has children who are not full-blooded italians thing that at the time even the bravest of the mob boss sons wouldn't have done (Tommy Gambino married Frances Lucchese);

A non-italian like tom hagen couldn't kill so easily a Chicago Outfit boss without the commission ok;

The bloodlust of Michael: the 5 families bosses killing, the murders of Frank Falcone and Tony Molinari, the Dons of Los Angeles and San Francisco, respectivelyand of Carlo Tramunti of New Orleans. No boss in the american LCN history has the power of whack some many bosses without any consequences.