We've talked about this before, but I would like to add something else to the discussion as to why Vito returned earlier than 1927; no signs of fascism.

Mussonlini had sent his prefect, Cesare Mori, to Sicily in 1925 with the objective of destroying the Mafia. So it would be a very risky and dangerous decision for Vito to return to Sicily while the Sicilian Mafia was in the midst of being eradicated. Especially considering that Vito himself was planning on killing a Mafia boss and his hench men. Second, in those scenes, if I remember correctly, we don't see any sign of fascism, no posters, no flags, no "blackshirts", no nothing. I think that by then, when the Fascists were trying to purify Sicily of the Mafia, fascism would have been visible in Sicily as well.

And not to mention ofcourse the little boy Michael, who could have been no older than three years old, certainly not sevens years old.

So in case you didn't know already, imo Vito's return in 1927 would be absolutely out of the question. FFC's own notes include that Vito returned in 1922 or 1923, depending on Peter Cowie or Harlan Lebo. Also, the original trailer of Part II specifically states that Vito returned in 1921. So I think the person who created the timeline should be hanged, or at the very least tortured for a couple of hours. What was he thinking?