What about “Battlefield Earth”? That movie ROCKED. 
(yes, I know I must be punished now. Please, be gentle).
I can’t believe nobody mentioned “Heavy Metal” that movie rocked. I think it was the best animated movie ever too. Plus it had a cool stories about the mysterious green ball in it.
Hey! how did Miller get my list?
Not seen so far: Clash Of The Titans, The Last Unicorn, and Flash Gordon (Oh, shut up).
“Flash!..Ah-ahhhh…”
What a compelling soundtrack!!! 
but Brian Blessed can do no wrong…
and I’d nominate Ladyhawke if some kind soul would rerecord the soundtrack without the cheesy synthesizer.
In addition to most of what’s been posted here, I’d have to include the animated Pinocchio. One of the all time great films, IMHO.
Jeez. Just about everything I thought of has been mentioned already, but I’ll put in my votes anyway.
Dragonslayer - I saw this movie again recently for the first time in years, and appreciated far more now as an adult than I did when I was a kid. It’s the first movie that came to mind when I saw the thread title.
The Princess Bride - This choice is almost too easy. Brilliant book adapted into a brilliant movie. It’s so full of great quotable lines.
Time Bandits - This was high on my list of all-time faves as a kid. Now that I’m older, I can see the flaws in it, but that doesn’t stop me from having the Criterion Collection DVD of this movie.
The Neverending Story - See my screen name. I’m pleased to see that it has been mentioned so many times in this thread. The movie is a reasonably OK adapation of the first half of the book. I will not speak of the sequels, of which I only saw the second and swore never to lay eyes on the third. If you’ve never read the original book by Michael Ende, you are missing out on the best parts of the story. It’s coming out on DVD soon, and I’ll be getting it. I’ve heard that it’s being adapted for a TV series, but my cable provider doesn’t carry the Odyssey Channel, which will be airing the series. CRAP!
Labyrinth - Haven’t seen it in years, but remember really liking it.
Ladyhawke - Saw this again some time ago on the SciFi Channel. Really great movie. Unlike Salieri2, I’m not bothered by the music.
Edward Scissorhands - Only one mention so far in this thread? Surprisingly good movie done as fairy tale set in suburban America. Part of it was filmed in my original hometown of Lakeland, Florida, which startled me the first time I saw it.
James and the Giant Peach - I grew up reading Roald Dahl. His books were awesome. This is a great adaptation.
Charlie and the Chocolate Factory - See my above note about Roald Dahl. Gene Wilder is perfect in this movie. I usually dislike musicals, but I’ve made an exception for this one. It’s got a mean streak, and that always appeals to me. I’ve heard they’re doing a remake of the movie, which I regard as nearly blasphemy.
The Dark Crystal - Parts of it are a little hokey, I think, but I really like this movie. There’s a mean streak here, too, as I recall.
The Adventures of Baron Munchausen - Cool, underrated Terry Gilliam flick.
I knew this would happen!
I would think of another movie just as I hit the “Submit” button.
Groundhog Day - I think it’s Bill Murray’s best work yet.
OK. Last time I’ll add something here…
The TV miniseries Gulliver’s Travels. I don’t know if the OP intended for television productions to be included or not, but I simply can’t resist acknowledging what I thought was a surprisingly good adaptation of Swift’s novel.
Absolutely 100% agree with you on this point. It’s the single problem with the movie - everything else is masterful, even if it is a little slow in parts. Dare I say it’s Michelle Pfeiffer’s best role outside of Batman Returns?
Anyways, a new soundtrack would be a fantastic idea - and wouldn’t be difficult to achieve. Who directed it? Ooh, Richard Donner did! That’s interesting, he’s all for Director’s Cuts and remastering for DVD. Hmm, let’s send him a petition.