It’s a great list, with a few underrated gems, but…
I haven’t seen all of those movies, but those I have seen were “underrated” for a reason. I’m a fan of The Dark Crystal (seen the movie several times, owned the novelization as a kid and read it multiple times) but it was kind of inaccessible to most audiences (too strange).
The Black Cauldron had a meandering plot that was hard to swallow and different things happened at different times for “because, that’s why” reasons.
Ironic, given the clip used in the list, but Atlantis: The Lost Empire had a lot of potential, but squandered it on cliched villains and New Age-y nonsense.
Similar objections apply to both Bedknobs and Broomsticks (one of my favorite films) and Legend: it’s all down to the story. Creature effects don’t matter—if the story is great, audiences will generally love a movie. If not, well the movie can slink off to the pile of “underrated” films.
Story. Story. Story.
It’s all about the story.