This book is great just because it is. It's just as good, in fact, as people think that Tolkien is. I can't speak for the sequels since I never read them, but DUNE kicks ass. And yes, I do like saying DUNE in all caps, because it looks important like that.
Arakis was entirely a new sort of place when DUNE came out, even if the other worlds were somewhat more boring. The sandworms are of course one of the big avatars of sci-fi, their sheer size and strangeness making them memorable supporting cast to the book. It's a bit sad how easily the Fremen ride them, but hey, who am I to complain?
Honestly, the Fremen were some of the more boring characters in the book. I much preferred reading about the other, more civilized people, with their politics of the Spacing Guild, Mentats, and Sardaukar.
Paul himself is a bit boring. Besides having the boring name of Paul, he's too amazing for his own good, and never seems to really step wrong. Plus the whole time you know that the Muad'Dib is going to win, so it's not a surprise when he does.
Oh well, it's still an awesome book, definitely worth the read.