I would have to agree that both Aragorn and Frodo could be Christ figures, although I would have to lean more towards Frodo. As Roa said, Frodo represents Christ bearing the sin of the world to be destroyed. Aragorn is more of a reach to me. He does go through the Paths of the Dead to bring salvation to man (or at least to the men of Minas Tirith
) but he doesn't die or suffer like Christ.
The symbolic representation that I see would be Gandalf as an angel and Saruman as the Devil. Gandalf and Saruman are both members of a high order, like the angels in Heaven. Then Saruman decides that he can be like a god himself, so he revolts, like Satan. However, he is defeated and cast down from the high place ( in the movie, he falls from Orthanc), like Satan from Heaven. If you're really creative, you can say that Helm's Deep represents the battle between the forces of Satan and the forces of God.