I'm not going to argue with Godfather fans, but I, too, am going with Layer Cake. Good call...proud of cfnet to see a post for it so early in the thread
I think there should be separate classifications for mobsters films and gangsters. best mobster: Godfather, untouchables, once upon a time in america, bronx tale, good fellas ganster movies chale carnal: blood in blood out, colors, american me, boyz in the hood. individual gangster movies: menace to society, scarface.
Despite all the other fantastic choices, I've always loved Donnie Brasco the best. I can't really explain it but that movie has more impact for me than any of the other big hitters. Johnny Depp is so great and it is refreshing to see Pacino play a different type of gangster than he usually does...and knock it out of the park.
I like the first Godfather a little better than the second for some reason, though I'm just going to rank them together as the best movie of all time. Gangster, mafia, whatever...nothing touches those 2. I love Heat and goodfellas. Scarface is kind of average for me.
Immediately stop what you're doing right now and go rent/buy/download Godfathers I, II and III. Watch I and II back-to-back...and then take III and throw it in the trash because that turd is awful. I once read a review that described III as reeking "like a burning house built out of chickensh!t and stuffed with dead dogs". Perfect. Seriously, if you like Goodfellas; you're gonna LOVE The Godfather.
Generational answers. Goodfellas sprung to mind, so I'm going with that. Eastern Promises was a damn good look at the Russian Mafia.
Couldn't have said it better myself. Nothing else is even close. The characters and just the story telling in these two films is absolutely amazing.