Looks like an auspicious post number for "Horse's Head" as well. Welcome.

I always viewed GF as michael's story. It has 2 angles to it:

1) Michael eventhough was on the correct side of the law, was kind of irresponsible in not supporting his father initially. When the key moment came, he fulfilled his responsibility as a son. That is the father-son aspect of this story that strikes a personal chord somewhere.

2)No one(probably except his father) took michael seriously. They viewed him as a kid who did not have what was necessary to run a family. With attack on his father, he was all the more in a weak position. From that stage, he went on to defeat his enemies and proved himself superior to others.This is the triumph of the under-dog aspect of michael's story.

Ofcourse all the other cinematic aspects like great direction, acting, music etc being perfect, it is not a coincidence that this movie is among the greatest.