On the harsh desert planet Arrakis, a boy faces off against Destiny with a capital D, in Frank Herbert's 1966 Hugo winner Dune. The reason it's a classic is that Destiny doesn't quite win.
Now that I've read both Hugo winners from 1966*, I can say with some authority that the most amazing thing about that year is that Roger Zelazny's This Immortal won at all — and I really liked This Immortal. But the cover of my copy of Dune — which, besides winning the Hugo, also took home the first Nebula Award — bears the tagline "Science Fiction's Supreme Masterpiece," and off the top of my head, I can't think of another novel worthy of the appellation. Yeah, Dune has its minor flaws, but they're so minor; the book is basically untouchable.