My partner watched it for the first time perhaps two years ago, and loved it. But it depends on what you consider a “good” movie to be, I suppose (story vs visuals vs characters vs …)
I think that will also inform whether or not this is a “good” series - what one considers “good” about Dark Crystal, and whether or not they kept that aspect in the series.
I had the pleasure of seeing a 35mm screening of it locally in a packed theater filled with kids (many of whom raised their hands when the manager said “who here has never seen this?”) and they jumped and laughed and gasped and squealed in all the right spots.
It’s a masterpiece of puppeteering and craftsmanship.