If the first Godfather film had been three hours of subtitled Italian, it would never have been successful enough to warrant a sequel.
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Thanks for the clarification. What I meant to say was that people don't like sitting through three hour movies in general, but adding the wonderful prequel scenes would have pushed it beyond Gone With The Wind length.
Personally, I don't mind long movies if they're richly dense, like Godfather, Gone With The Wind, Amadeus, etc. Reading about decisions in the movie making process, lots of movies get edited down not because certain scenes aren't good or drag the pace, but simply to get the movie under two hours.
Is very bad to steal Jobu's rum. Is very bad.

The Godfather WAS a 3 hour film. It would have been 4+ hours with the young Vito scenes.
Coppola has said he would have had little interest in a sequel if he didn't have the young Vito portion of the book to work with.

I think contrasting the Young Vito scenes with the Michael scenes as they assert themselves into their worlds and come into prominence was masterfully done.
I don't get much from the contrast between young Vito and Michael, but I'm sure The Godfather would never have been made if the young Vito scenes were included in the original screenplay. People don't like sitting through 3 hour movies. Once The Godfather became a hit, they had much more capital to deal with with the sequel.
I like II, but the young Vito part is FAR more interesting and enjoyable to me than the Michael scenes.
Is very bad to steal Jobu's rum. Is very bad.

I disagree. I think contrasting the Young Vito scenes with the Michael scenes as they assert themselves into their worlds and come into prominence was masterfully done.
Television is a vice; film is an addiction.

You would like The Godfather Saga. They took 1 and 2 and combined it so that it would play in chronological order.
It was on HBO go but I think it moved to Cinemax.