I've often wonderered about Vito's "lost years":
The novel says he was 12 when he was sent to America. He "boarded with the Abbandandos" and worked in their grocery store. It's not inconceivable that a 12-year-old would work in a store at that time. But Vito's about 9 when he flees Sicily in the movie, and the next we see of him, he's married, in his late 20's (at least) with kids, and working in the store. It would have been interesting to know what the Andolini/Abbandando connection was, and what Vito did in those "ost years."

But I really don't need to know more about Genco than what I saw in II.