That's a tough one. I think it depends on what side of the mob you want to see, the top or the bottom. For the top of the chain, The Godfather is the best of all, for the bottom it's Goodfellas. Of the two though, I'd have to side (by a very, very slim margin) with The Godfather. It was the film that got me interested in films as art so there is a nostalgia factor with it. It's majesty and opulence and overall tone make it slightly the better film.