Dune (talking about the book) is so many things. Aside being scifi adventure story and power play like GoT or Godfather, it gets to so many themes: society, religion, evolution, economy, ecology, and how all of these interact.
I feel the biggest idea is speculation about to what extremes a human being can be developed and evolved, physically and mentally. There are variety of superhero like capabilities. Some of those slip to scifi/fantasy, but many are a good question of how far could human go. And this gives characters that are admirable the same way as Sherlock Holmes or Batman. Which is what's wrong with the new movie (still haven't seen 2), these pinnacles of humanity have been nerfed to whiny b*tches.
Yet every character is somehow slightly flawed, whether by guilt, obsession for duty, cold bloodedness, arrogance... (Duke Leto is the only really too perfectly good person. But even for him, I mentioned obsession for duty; Atreides could've gone renegade and avoided all of this happening...)