After recently seeing the 2013 documentary about Alejandro Jodorowsky's plans for a film version of Dune back in the 1970s, I decided to check out the commentary online.
As it happened, the consensus view (corresponding to those interviewed within the documentary) seemed to be a wish that it had been made and they could have seen it--and that it would have been a triumph which would have put science fiction filmmaking on a different course.
Granted, particular ideas were dazzling. (The opening long take Jodorowsky described would have been epic.) However, given the degree to which it deviated from the letter and spirit of the original novel (indeed, Jodorowsky's predictable disinterest and even inversion of its themes), it would not have been a definitive version of Herbert's books--or even a really satisfactory one.
More importantly, the chances of its having been a successful film, even on an artistic level, strike me as having been vanishingly small. I will admit that my attitude toward the Modernist/postmodernist aesthetic, and still more, its underlying assumptions grow increasingly dim.1 (Increasingly I feel as if a very large part of our artistic and cultural life has been in a cul-de-sac for a hundred years.) But all the same, I will say that even dazzling bits do not make a successful whole. And taken altogether the movie could easily have been unwatchable. Consider how David Lynch's 1984 version has been received, despite its dose of weirdness being far, far milder than Jodorowsky's not just much longer, but astronomically more surreal, gruesome, garish conception. (The idea of a freakishly made-up Orson Welles overseeing and completing the graphic dismembering and beheading of David Carradine just about says it all in this regard.)
Perhaps the best and worst that could have been hoped for it would have been its becoming a cult film, a curiosity--which is a very different thing from its replacing Star Wars as the defining science fiction film success of the period. Indeed, it may have wound up more influential in not getting made--in that bits and pieces were taken from it and utilized in other, more plausible work (most famously, the H.R. Giger drawings that became the foundation for the Alien franchise).
1. Shameless plug time: because much of the history of science fiction makes little sense unless one gets all this (and frankly, even the professional critics tend not to), I discuss these matters at some length in Cyberpunk, Steampunk and Wizardry. Why not go and check it out?