The 3 original films in their separate original forms on 6 discs:

Godfather (1972)

Godfather: Part II (1974) 

Godfather: Part III (1990)

Plus a supplemental disc with 73 minute documentary on disc 7 "The Godfather Family: A Look Inside"

LaserDisc Database Godfather 3 contains the final Director's Cut with 9 minutes of additional footage.