And really most of the novel was covered in I. But Puzo was a screenwriter for II so he basically wrote the before and after for I.
I still default to I as the best because as much as I love DeNiro, nothing to me tops Brando as the older Vito Corleone.
Actually, the novel had the wrap-around. It starts in the middle. I think the BALANCE is a bit stronger in the movie, between the three time periods, but the storyline is there in the novel. I've had this conversation with multiple people on the board, I had a Management class at UM where our "textbook" was The Godfather (novel). No joke.
The reason I like I as much (if not better) than II is because of the classic time period of the mafia, when there was still some honor and intent behind their practices. I am not nearly as enamored of the mafia of the "60s and 70s and beyond", it is also the reason why I was not as much of a fan of III.
Don't get me wrong, I loved Hyman Roth and Moe Green and Frankie Five Angels, but to me, the decline of omerta and honor in II was depressing. And I think Sonny's storyline, while brief, is completely emblematic of an ongoing problem that the mafia had, the hothead who can't keep things under control for the sake of the business.
Plus, there were just a few extra ALL-TIME CLASSIC Godfather moments in I more than in II.
---Bonasera asking for his favor
---Luca Brasi practicing his speech
---"YOU CAN ACT LIKE A MAN!"
---Michael describing his father to Kay
---Jack Woltz and his infamous double-racial-slurs
---The horse head
---Luca Brasi sleeps with the fishes
---The worthlessness of Fredo when Vito is shot
---"Leave the gun, take the cannoli."
---The high drama of Michael protecting Vito at the hospital, including Enzo the Baker (who was the subject of the OTHER big "Connie's wedding" favor, shown in the book but not in the movie)
---Michael's meeting with Sollozzo and McCluskey
---Michael's offer to Apollonia's father
---Sonny's fight with Carlo
---Sonny's shooting at the tollbooth
---"It was Barzini."
---"You're not a wartime consigliere, Tom."
---"Don't ever take sides against the family."
---The OG "settling of all old Corleone family business."
---Michael assuring Connie that he would not kill Carlo.
---Closing the door on Kay.
Come on, now, every one of those elements is ******* CLASSIC.
That's what puts I above II for ME PERSONALLY.