I think this film is way way underrated. Yes I agree it's a real shame that they didn't go with Jorodowskys version of Dune, but let's face it, it would have been near impossible to produce a 14 hour film with all the talent and special effects he wanted to include in it today let alone back then.
This films is by no means perfect, but I will say that it is infinitely better than the boring and frankly 2 dimensional Star Wars A New Hope.