[Parmawen]

Well, on surface level it would appear Frodo is more of a hero than Sam, as it's to him that the direct task of destroying the ring falls on.

But really, I agree that it's Sam. It depends on what the definition of "hero" is. According to dictionary.com (I know, not the trustiest of resources) the two most applicable definitions are: 1. In mythology and legend, a man, often of divine ancestry, who is endowed with great courage and strength, celebrated for his bold exploits, and favored by the gods.
2. A person noted for feats of courage or nobility of purpose, especially one who has risked or sacrificed his or her life
These are more descriptions of Frodo, but according to Tolkien, it's Sam who's the real hero. I think that's because in Tolkien's mind being a hero is more of a sacrifice. One of the things that Sam loses is his innocence, he's awakened to the harsh realities of his world by the trip to Mount Doom. But maybe the act of being a hero is the ability to still function after that. Despite this sacrifice, Sam can move on, fall in love, and hangs on to his optimistic outlook on life, even though he's suffered so much. It's the difference between Frodo and Sam, for Frodo is changed just as much...but he becomes mellow, subdued, and while we don't really have a clear access to his thoughts before leaving for the Gray Havens, it is obvious that there has been a major change in his countenance. He is more melancholy and reminiscent. Yet Sam still has in his heart the capacity to love and to live in this world. While it may just be because he was not so tainted by the ring as Frodo was, it still shows an aptitude and attitude that reflect on him as a hero, because he has hung onto that shred of optimism that within, courage and strength lie.