I like to think of LOTR as an "dual epic." An epic requires that there be one central character that is essentially superman who through the course of the work achieves greater and greater stature until he reaches the top of the mountain so to speak. If he happens to die which does fit within the convention then he goes out with a bang and it's for a noble cause. In LOTR you have two superman characters, Aragorn and Frodo. Aragorn is the more traditional epic hero, but Frodo still incorporates enough of the conventions despite the fact that he's a little hobbit and repeatedly gets his ass handed to him by all sorts of creatures. While he doesn't necessarily vanquish his opponents he always manages to keep going until he reaches his goal, and then (without trying to spoil the movie) he must continue to ascend and reach for new heights. Plus we have all these supporting characters that for the most part all have some kind of obstacles placed in front of them which they triumph over in one way or another. I could go rambling on and on but yeah that's the basic concept.