First, it is important to note what the Christ figure is. Christ is one who sacrifices himself for the sake of others. In particular, a Christ figure experiences death and resurrection.
From this description, there are many Christ figures. Anyone who sacrifices himself or herself is a Christ figure. All the members of the party that go to Mordor is a Christ figure, because they are sacrificing themselves on what appears to be a suicide mission. This take courage and love for others.
However, from the perspective of death and resurrection, there are a few others that fit the definition of a Christ figure even more. Gandalf stands out in his fight with the Balrog. He fought the Balrog of Khazad-dum and he perished along the way. Eight days later he reappeared, but this time he came back as Gandalf the White. In fact, he was even more powerful. There was a death and resurrection.
The same can be said for Frodo. At the end of the novel, he is no longer the same. He will never be the same. He had to carry the ring and the ring changed him. His sacrifice and courage though saved Middle Earth.