Consequently, most films based on a book are worse than the book.
Neither Dune film is an exception to this. I'd rather just read the book again than watch either film. And if you're someone who has never read the book, and indeed has no desire to read the book, then why do you even need a "Dune" film made for you?
What's truly sad about Hollywood is the complete lack of original film ideas.
It's a hard decision for those making a movie, you either push for your own vision and risk alienating book readers, or you are faithful and risk making something soulless and derivative.
Of course there are exceptions. But I think the majority of exceptions lies on directors adapting unknown books (like Hitchcock), or perhaps books with less-rabid fanbases.
The movie we got was _blah_, but does have one of the most visceral moments I've seen in any zombie flick: the bit where Brad Pitt stands on the edge of the roof, counting down the seconds until he'll know whether he's been infected or not.
That wasn't what I was talking about – some imaginary filmatisation which has nothing to do with the book. I was talking about not staying true to the "author's vision". You can make a Dune movie in many ways. You can have the same characters, ornithopers and main events, while having a completely different vision for it.
Dune is also a book full of ideas. You can play up many different angles – ecological aspects, loyalty to leaders, political drama, religious fanaticism, etc. – while still being very much a Dune filmatisation. And a film maker can put their own spin on any of those, or bring up their own topics which makes sense to treat within the Dune framework.
Sure, for the money people, being a Dune filmatisation means people will see it because they know that Dune is a famous book (irrespective of weather they read it). But only die hards who have read the book (and have a very immature view of film as a medium) would judge it for how true it stays to the author's vision. The rest will be happy if it is a good movie.
Note also that Lynch's Dune influenced the later books!