The movie brought home the concept of the eternal hero very well, I thought. Here, the hero is not remembered for all time because of his singular accomplishment, but because his story is repeated over and over. There's nothing singularly good about the hero- he's subject to many of the same impulses and vices of everyone else. He's unique because we recognize the universality of his situation, not because we think he's braver or wiser or stronger.
I don't think many people want to be Beowulf (although I think the person who was quality control for the animation scenes of Grendel's Mom probably really loves *their* job) even though he has all the qualities one might expect to want: strength, wisdom, a bevy of bedwarmers. The hero is unusually blessed but also unusually cursed: having the power on average to make really good decisions doesn't free you or enable you to prevent youself from making bad decisions, too. There's also the idea of scope: as you power grows, your decisions become higher impact. Beowulf first comes to the community leading only a small band of Geats: he makes powerful decisions and is largely victorius; but makes mistakes too, and gets most of his men killed. Later in life, he is King, and his decisions (both past and present) both reward and endanger not just the small heroic raiding party but the entire nation he rules.
There's another idea of scope that I thought the movie captured very obviously but well executed: that the problem at hand is often not the problem. I'm not intending to put a Manichaean spin on the plot elements: I don't think that it's a battle between absolute good and absolute evil. By saying things like "unusually blessed but also unusually cursed" one might think that both are flip sides of the same coin, but I don't think so: I think decisiveness is a good, not also an evil. Limited perspective is an enabling factor, sometimes: if we constantly sought to be the most correct, we'd likely be paralyzed by the level of effort any activity entailed. We make mistakes, hopefully calculated, to be decisive. None are immortal: Platonism is a myth. We make mistakes because time is constantly moving. Sometimes we have the time to think things out, but not always. The hero rises to the call of enhanced outlook or ability or insight, but also accepts the fact that all perspective is narrow; the hero will be called to pay the price of heroic decision.