Yeah, I watched both for the first time recently as an adult, and I wouldn't split the movies into good/bad. Labyrinth works well as a modern fairy tale written by a girl on the cusp of adolescence, and Connelly is as engaging as she usually was in that era as the young protagonist. Questionable costuming aside, Bowie's performance is iconic, and the Muppet work and landscapes are as memorable as you'd expect. (While we're at it, Connelly fans might want to take a look at Phenomena, a Dario Argento horror movie starring her from the same period. It's far darker than Labyrinth, but I've always thought of the movies as twins due to the fairy-tale aspect. Bonus: It was the primary inspiration for the Super Famicom Clock Tower!)
Dark Crystal, on the other hand, is very oddly paced (Labyrinth also has this problem to a lesser degree), and it does take a long time for the actual story to get going. It's also fighting a lot of cliche (take a drink for every one that opening narration mentions and you'll be drunk before five minutes are up). It does reward attention, though, as every corner of the frame is packed with unique sights and details - the composition and framing is really painterly. Also notable: the active role played by the love interest was considerably ahead of its time, and there is some gory, screwed-up **** in this movie. The death of the Skeksis emperor - good Lord. For various reasons mentioned, it might not hold every child's attention (might scare a good number of them bloody off); it's better seen with an adult's eyes.
TL/DR: Both movies are worth seeing.