Here are some books I liked and some I sort of liked. Mostly children's fantasy here, but there's some variety.
- Anything by Diana Wynne Jones. The Chrestomanci series, Archer's Goon, and Deep Secrets are some of her best, but they're all quite good.
- J. K. Rowling's Harry Potter, of course.
- Patricia C. Wrede did some very nice stuff. Dealing with Dragons and the rest of that series are probably the best, but the Lyra series is also good.
- C. S. Lewis' Narnia series (The Lion, the Witch, and the Wardrobe) et al. are good.
- JRR Tolkien's Lord of the Rings trilogy is the best thing ever, and The Hobbit is also very good. Try the other books as well if you're into some more information-laden stuff.
- Pamela F. Service mostly did more sci-fi and such, but there's Winter of Magic's Return and its sequel. All her stuff that I've seen is worth a read though.
- For very punny (and sometimes a bit sexual) stuff there's Piers Anthony's massive Xanth series.
- Lloyd Alexander's Prydain Chronicles.
- Not really children's, but Robert Lynn Asprin's Myth and Phule series are very good.
- John Bellairs wrote some of the scariest books I've read. (Not that I've read much horror.) Made me laugh when I heard about how RL Stein was 'too scary' for kids.
- Lewis Carroll, of course. Not just the Alice books, but also Sylvie and Bruno plus its conclusion.
- Madeleine L'Engle's A Wrinkle in Time series is nice.
- Susan Cooper did some okay stuff. The Dark is Rising and Under Sea, Over Stone are worth reading, but I got bored as I went further through the series. The Boggart is good though. Also decent is The Boggart.
- Terry Pratchett's alright, though not a children's book. (Not meaning children that shouldn't read it!) Good Omens by Pratchett and Gaiman is perhaps the best. Very Good. Johnny and the Dead and it's sequels are also very good.
- Roger Zelazny has done a lot of stuff. The only one I've read is A Night in the Lonesome October. It's truly a bang-up story.
- Katherine Roberts' book Song Quest of the Echorium Sequence is quite good. I haven't read any others in the sequence, unfortunately.
- Gail Carson Levine's Ella Enchanted and The Two Princesses of Bamarre are both very good.
- Roald Dahl did a lot of good stuff. The BFG is one of the especially good ones, but they're all great (except for Boy and the one about him being an airforce pilot.)
- Eoin Colfer's Atemous Fowl books are surprisingly good. I haven't read his other stuff yet, but The Supernaturalist looks like it may be worth reading, though probably more scifi than fantasy.
- Jenny Nimmo's The Children of the Red King series (Charlie Bone) is a very nice rip-off of Harry Potter. I wish they were much longer and more verbose, but they're very good as is.
- Suzanne Collin's Gregor the Overlander is decent.
- Christopher Paolini's Eragon (and sequels as they come out) seems like a decent Tolkein-esque fantasy, though if you're into the technical aspects of writing you may find it appalling. The rest of us can revel in our ignorance.
(I've written reviews of some of these books. I'm planning on writing more and posting them later.)
I've been told that Brian Jacques's Redwall series is also good, but it's been so long that I don't remember them well at all. I found them boring, as I recall, but I'm planning on re-reading them eventually.
Google Sets seem to recommend Vivian Vande Velde and Garth Nix, but I'm not so sure about Nix.
If you know of some you think I'd like based on this list, please do tell me.