I didn't mind the Preludes trilogy. In fact, there's a scene in House Harkonnen (I think) which has stuck in my mind and made me vow to destroy any Harkonnen I ever meet. The Denis Villeneuve films could do with that sort of scene as currently I don't despise the Harkonnens in his adaptation the way I feel I should.
The Legends trilogy I managed to get through by sheer determination, but the rot was setting in and I only managed half of the first sequels book before giving up.
Bearing in mind that I didn't really think too highly of Heretics and Chapterhouse, but I haven't given them a re-read for many many years.
20 year old me just got a little bit excited. 40-odd year old me is sad that he's never going to fit back into his leather trench coat.