Minor point - whilst Lynch's work certainly frequently looks like it was drug-assisted, Lynch is actually not at all a fan of drugs as a creativity aid:
http://www.goodreads.com/quotes/498489-we-all-want-expanded-...
He just has a remarkable vision and ability with the weird.
That's a really low bar. A better comparison would be the three-part Dune miniseries that came out in 2000, one in which Lynch's version doesn't fare very well.
For example, watch the harvester-eaten-by-worm scene [1] [2]. Which of the two has stood the test of time? I could watch the 1984 version over and over again. Everything about the 2000 version - even the timing of each shot - is uninspired and dated, almost like a Westwood Command and Conquer in-game video. Watch how much more engaging the storytelling is in 1984 in this essentially dialogue-free chapter.
Lynch's version, for all its flaws, is still watchable.
The Lynch movie has, like most Lynch works, a strange atmosphere that in this case helps highlight the changes that Paul is going through as his consciousness expands.
That said the children of dune miniseries fares much better, but maybe because there isn't anything to compare it to.
The book heavily references the middle east, and oil dependecy.
The movie has zero, or at the least, very little visual symbolism. Especially if compared to Lynch's other work.
Drug assisted is the last thing I'd say about either the book, or movie.
I dunno about the movie, but I have heard sometimes that Herbert was quite fond of helping the creative process by those means.
http://dailygrail.com/Shamanism/2014/7/Magic-Mushrooms-were-...
It's not a terrible film. Not by a long way.
It's a difficult film. It's risky. It's not entirely successful.
But terrible? Wisecracking CGI Superheroes Episode Number Actually I've Lost Count Now is a terrible film. (One of a long, long series.)
Men With Guns and So Very Much Shooting is a terrible film.
Too Many Explosions Looking for a Plot That Isn't All About Running and Shouting is a terrible film.
Dune was one of many drug-assisted weird things that fell out of the 1970s and never quite left. It's not a terrible film - it's a museum piece.