The '84 version was a huge disappointment, especially for fans of the books.
McLaughlin, Prochnow, Annis & Madsen were okay (IMO) but some of the other characters were horribly miscast.
(Patrick Stewart is a hugely talented actor, but he was just not a believable Halleck and the idea of him stepping into the arena to avenge the death of his sister was just kinda sad even at the time...)
Awful, but quirky movies (e.g. Barbarella, Rocky Horror, Plan 9 From Outer Space, etc) often attain a cult status over time and the '84 Dune falls into the same niche, but in this case, the special effects were so bad that even aficionados affectionately refer to the worms as, "Turds with teeth."
Even the cooperation of Frank Herbert himself in the screen adaptation couldn't save it.
I thoroughly enjoyed the '21 version. From big things, like the casting and visual effects to minor details, like the length of the knives being appropriate for the style of fighting, it was much better. (Again IMO)
Part II has been officially green-lighted