I just think The Godfather is much more than a Gangster movie. It encapsulates themes of family, love, loss and how power corrupts. 
Many people agree with you. The Godfather was the highest grossing film of 1972. It also was the highest grossing film ever made for a long time.
And I personally think it's easy to see why. For a movie almost 50 years old, it absolutely holds up. The actors and cast are superb and visually it is still stunning. It also has that iconic soundtrack.
It is an extremely influential movie. This movie has been deemed to be historically and culturally significant. It's actually currently ranked as the 2nd greatest film in America. The top film is Citizen Kane. 
That's interesting. It also makes me feel rather guilty as I've never seen Citizen Kane, perhaps I will soon. I think the journey and transformation of Al Pacino's character Michael, is endlessly fascinating and so well portrayed by the great man.
He did a great job. Clearly, the movie was a huge success. The Godfather has been nominated for eleven Academy Awards!
Yes it certainly was! I can see why too, it was obviously worked on by many very talented people, making several of the cast household names. The sequel is equally excellent too I think. 
It definitely was. One interesting fact about The Godfather is that the directed Francis Ford Coppola was the 13th director to be offered the job, and he took it.
That is very surprising, I never knew that! Particularly given how good a job he did and what he has gone on to achieve after The Godfather. Apocalypse Now is another of my favorites. I have never read Mario Puzo's book but I intend to.
Marlon Brando actually won an Oscar for The Godfather that he refused to accept.
Yes I heard about that, he was such an interesting person. Yet another thing that makes this movie so fascinating. I believe he put many of his own ideas into Vito's character such as the unique voice and way he talked.