Just finished the Lord of the Rings (umpteenth re-reading), and I was thinking; there's something about fantasy written by Christians that you don't get in other books.
Concurrently, I've been reading other books, as is my wont; a bunch of Dick Francis and other things, but also some fantasy such as George MacDonald's The Princess and the Goblin*, and Philip Reeves' Scrivener's Moon.
The latter is set in a fascinating and very well realised world, with a lot of interesting ideas. But although there are a lot of good SF & fantasy books, what Tolkien and MacDonald have is something solid underneath. Neither book is explicitly Christian - nor would I agree with all of the writers' theology. But (and I'm probably misquoting C.S. Lewis here) the message of a story comes from the whole cast of the author's mind - they don't have a 'moral' but truth and wisdom permeates them. And you discover more each time you read them.
Of course, that's not to say that non- Christian authors can't write truth or wisdom, and many of my favourite books are written by non-christians, but at the end of the day, anything without an eternal perspective falls short. Nor is it, alas, to deny that there's a lot of shallow drivel written by Christians!
*Which is not a patch on its sequel, The Princess and Curdie.