By the way, it should also be noted that the ending was probably inspired by the ending of THE SEARCHERS where we see Ethan walking away while the door closes in front of him. Our viewpoint is from inside the house and the door also turns the screen to black.

It saddens me to hear how someone would not appreciate the ending of THE GODFATHER due to too much exposure to mainstream movie pap. The best movies aren't those that tie everything up in a nice neat knot. It leaves nothing to discuss because the movie already tells you how to think and feel. Great films often ask as many or more questions than they answer. They give you something to think about and often linger in your head long after the movie's over. That's why there's so many more websites devoted to movies like THE GODFATHER or, say, CITIZEN KANE than something like HOW TO LOSE A GUY IN 10 DAYS.

I'd also like to point out that incredible expression on Diane Keaton's face as the door closes when she realizes what her husband has turned into. It haunts me for a long time every time I watch it and I feel great sympathy for her. That's a powerful scene.