My thoughts on this are that despite the parallels and inspirations, the treatment is radically different. Dune is a much more adult, spiritual work, less concerned with derring-do thrills and spills. Star Wars by contrast is first and foremost a fantasy (rather than science fiction), inspired by thrill-a-minute Saturday matinee serials like Flash Gordon, borrowing a little from Dune, yes, but also just as much from The Lord of the Rings, Arthurian legend, The Wizard of Oz, biblical stories, other religious narratives (there's a fair bit of Hinduism and Budhism in there too), westerns, samurai films, the writings of Joseph Conrad, and more besides. Star Wars served almost as a kind of melting pot summary of cinema history to that point, before taking these ingredients and turning them into something new (to use a scientific metaphor, a compound) via spectacular light-years-ahead-of-their-time visual effects, sound effects, and so forth, but anchoring them in the familiar cues of silent cinema (including John Williams's magnificent heroic score fulfilling the role of the musical accompaniment). The finished product really is vastly different to Dune - either the novel, or any of the wretchedly subpar adaptations we've seen to date (though I hope Villeneuve manages to crack it).