I'll be frank here: I dislike Christian fantasy. Actually, I dislike all fantasy that preaches at you, whether it's religious (Christian, Wiccan, vaguely-spiritual-with-no-real-commitment-but-disgust-for-organized-religion), anti-religious (Philip Pullman, Christopher Paolini), political, or whatever the hell.
The fact is, there's just not that much good Christian fantasy out there... and I think this is because sub-par crap like Paul's is accepted and promoted by Christian publishers just because they're really desperate to find material that American Protestant parents will accept without question. So stuff that regular publishers would say "Sorry, not working for us" because of QUALITY will get put out anyway.
So heres some stuff that IS good enough.
Okay, I'm stretching the definition of "Christian" fantasy here, but honestly Tolkien's religious beliefs really shaped a lot of stuff about his fantasy world. It's just that there was a lot more to it than just that, such as his love of Norse myth and language. But there's definitely a lot of his Catholic beliefs and morals in these stories, through the depiction of the Elves and the character of Gandalf, and the values that he infuses in the good guys.
And the Silmarillion is basically the Bible of Tolkien's world, describing how the world was created and where all the various fantasy races and creatures came from, along with thousands of years of wars, conflict, corruption, love stories, and tragedy. It's epic stuff, but not light reading. And it has a helluva lot of worldbuilding with angels, the afterlife, and stuff like that.
Okay, technically this is not CHRISTIAN fantasy but it's written in a comparable style to The Hobbit. It's funny, weird and full of faerie mischief, plus there's a murder mystery and a bunch of kids who just frolicked away into a fairyland. You will never find another book like this one, and that's a shame.
Chesterton is somebody who would probably be better known in today's society if he hadn't been a theologian - the guy could be insanely funny, weird and silly, and while not "fantasy" in the typical sense of the word, these books are odd enough to be considered fantasy. One is a story about a 1984 (Chesterton apparently thought technology was overrated) in which England is ruled by a king selected at random, and some guy decides to have fun with it; the other is about a strange little gang of anarchists riddled with double agents.
Yeah, Lewis' name is pretty much synonymous with Christian fantasy, mainly because of his classic Chronicles of Narnia series. Even people who aren't religious often love these books, just because they have that charming Britishy 19th-century tweeness that a lot of people try to have but fail at. The last book is a huge downer, and kind of controversial, but the others are delightful - including the prequel and midquel. They can be a bit hamhanded at times, but they're also very whimsical, funny and one of the first examples of fantasies that involves a multiverse.
And then we have the Space Trilogy, which... is actually sci-fi, but is also kinda fantasyesque at times. These are much more serious and thought-provoking than the Narnia stories.
This is another one of those authors who doesn't immediately make you roll your eyes and go, "Oh hell, not another preachy one." This guy actually takes a lot of care to write a complex, vivid story in a very unusual setting, more Patricia McKillip than anything else. There are some little glimmers of Christian theology here, but they're embedded in a really brilliant story.
Stephen R. Lawhead
Stephen Lawhead is sort of the anti-Marion Zimmer Bradley, in that he writes pseudohistorical/fantasy works with a Celtic twist, but preachiness is kept pretty low.
For one thing, here is his Arthurian series, which starts in Dark Ages Britain and Atlantis and progresses all the way past Arthur's death. I can't quite get into the present-day reincarnation story, though.
And then we have the Song of Albion series, which mixes modern-day characters with a magical, frightening world called Albion which is full of Celtic myth and legend. Sort of like a Celtic Narnia, but for older readers.
And finally he gives a special spin to Robin Hood legend in his King Raven trilogy, which mingles fantasy and historical fact, and sets the outlaw hero up as a Welsh prince who has had his lands taken away and his father killed. Mystical stuff ensues, and you can guess what happens then.