In the prison bible study we talked a lot about Gandalf. But we decided that, while Gandalf is a critical player, his main job is to clear the ground so that men and hobbits have space to operate.
We concluded that Gandalf is sort of like Michael the Archangel. Gandalf fends off higher demonic powers, like the Balrog, so that men and hobbits are able to carry out the decisive action on the ground. Gandalf doesn't confront the Dark Lord directly, but he makes room for others to defeat him.
Frodo seems to be the main hero. And I'd not argue with anyone who believed that. But the men in the study had a different opinion. In their estimation the main hero of the story is Sam.
At multiple junctures Sam is the one who saves the day. And the story ends with Sam.
Critically, when Frodo can no longer climb Mt. Doom, Sam picks him up and carries him.
Again, this goes to the deeply Christian heart of The Lord of the Rings. The main hero is a servant. We defeat evil by carrying each other.
Yes, Frodo is the dramatic focus. But if The Lord of the Rings is anything it is a prolonged meditation on the fidelity of Samwise Gamgee.
Which is to say that The Lord of the Rings is a prolonged meditation upon sacrifice, selflessness and servanthood. Sam never thinks of himself, never puts himself first.
And at the end of the movie all our attention is on Sam. The hero of the story.