Well, I think one of the things that makes The Godfather unique is Coppolla’s treatment of the family members. Once you start thinking of them as likeable human beings, they then do things that make you realize that they are monsters. Like Michael-joins the Marines and becomes a war hero-then returns and brutally murders the Turk and Captain McCluskey. Later, Michael is in church, participating in a baptism…which culminates in the murders of his brother in law and other enemies.
Not the kind of people you want for friends and neighbors!
A lot of the film deals with the ambiguity of good and evil.
I love the book. The movie…? I like it, but nowhere near as much. The pacing is hard to deal with, and you just don’t “see” as much into people’s mindsets as you can in a book. Plus, it’s not my favorite genre. I will happily sit through three hours of LOTR, but not necessarily Godfather.
The movies were long, boring, and portrayed characters I didn’t like. Most of the actors are ones I’m not fond of, either. I’ve seen the movies once. I have no desire to ever see them again.
The problem I have with the movie is that the story is a tragedy but the movie is glorification. The story is tragic because while the Don claims he is doing everything for his family, his actions ultimately lead to the murder of two of his sons, his daughter acting shamefully, and his surviving son turning into a monster. However the star power of Brando and Pacino, along with the lush depictions of wealth overwhelm the tragic aspects and end up glorifying mob life.
That is a weakness of the movie. But I think that The Sopranos glorifies gangsters even more than The Godfather does.
Honestly, I’ve tried to watch it, but I simply cannot get into it. 30 minutes in, I’m bored out of my skull and I start looking for something else to watch. I realize that The Godfather was probably the movie that really started the whole mafia movie craze and it’s wonderful, the acting, all that, blah blah blah blah. Bottom line, it’s still just another mafia/gangster movie and those have simply not ever appealed to me much. I could sit through it.
But it sounds like your friend is weird.
Rape scenes. If there is a violent and graphic rape scene in the movie, I will either leave the room or turn the channel/cut off the movie. I don’t even care if it’s relevant to the plot, it’s gratuitous to me. I don’t need to see it.
I’m not a big fan of sports movies, because they all basically have the same plot (the underdog wins… eventually). So rarely do the champions just keep on kicking ass and the underdogs just keep failing until they give up. I’d pay good money to see a movie like that. 
I’m not a big fan of war movies either, but that’s about gratuitous violence. Because I have no compunction whatsoever about a good bloody vampire or slasher film (or anything directed by Quentin Tarantino), I cut myself a hypocrisy break and will sit through war movies from time to time.
I have to list The Godfather as one the most, IMHO, over-rated movies of all time.
It drags. The acting goes from wooden to hyperbolic. The story meanders. The score and the cinematography are the only things about the move I do like.
“And as to length, I feel that if a director wants to make a four hour movie and can make it compelling, then I’m all for that.”
So am I, I just don’t find that to be the case here.