The juxtaposition of young Vito building the family and Michael tearing it apart continues the corruption arc of Michael's character and adds a refresshing new layer to the film's story and pace (whenever it seems like it's about to get boring it cuts to young Vito and quickly picks up again).

Robert De Niro is the easy standout, but I have to give credit to John Cazale for his heartbreaking (get it?) performance as Fredo. The scene where he says he's smart and wants respect alwas hits me hard.

Also, I've never see as much geniune rage in an actor's face as in the scene where Michael fights with Kay. Al Pacino is beyond incredible.