I saw the movie version of The Lion, The Witch and the Wardrobe the other day, and I was left feeling that it was only so-so, and that it was a very accurate translation of the book to the screen.
The child actors were all competent-to-good, the CGI and special effects were even better than the Lord of the Rings series, and Liam Neeson made a pretty good Aslan.
One thing I certainly wouldn't have gotten out of it, if I had been 10 years old again, would have been any understanding that it was meant to be inculcating Christian values in me.
I read the entire Narnia series repeatedly when I was a kid, and some of them I re-read even in my teens. As fantasy children's literature, they hold up well, delivering the perfect wish-fullfilment story. Each book follows two or three of four human children from Earth (well, England) to a magical realm, in which they are hugely significant and heroic, interact with talking animals and mythological creatures, and learn valuable lessons. The last part is without a doubt the least important draw for most young readers.
However, they are also meant to be a Christian allegory. Aslan is Jesus/God - mostly Jesus. In The Lion, The Witch and The Wardrobe, he goes through a very brief via dolorosa and is then sacrificed for the sins of another. There's even a Judas figure: Edmund, who sells out his siblings for Turkish Delight.
I can't comment on how this allegory works for readers who were familiar with it from the start, or who regularly attend church and Sunday school before reading the books. I can say how it affects those of us who grow up in non-believing households.
Not at all.
I didn't realize there was any religious significance to the Narnia books until years after I'd read them all, when I read about it in another book. So, while the Narnia books may have some meaning for children who are already Christians, they are worthless as a missionary tool. The allegory is just too far off the mark to get across.
Think about it. The first time we meet Aslan, he's marshalling an army composed mostly of fauns, centaurs and talking animals. He's a big damn talking lion, who advises Peter on how to clean his weapons after killing a wolf. How is this anything like Jesus? Later, when he gives himself up to save Edmund's whiny little butt, Aslan is shorn of his mane, tied down and sacrificed by the figure who represents the Devil, the White Witch. She doesn't tempt him - indeed, Aslan is presented as entirely divine throughout the books, with no human qualities aside from an occaisional tendency toward rage. (Not at moneychangers, though. Currency exchange and temples are left out of the books entirely.)
Having been resurected (both book and movie make his resurection seem more like a magical trick than a divine miracle) Aslan goes back to being a ferocious general. If I had to pick a god similar to the big kitty, it might be Odin, Thor, Mithras, Thoth or I could even compare him to the cult of Adonis. Those were figures who either died and returned, or represented both healing and war. And they would have been entirely appropriate to surround with giants, ogres, centaurs and other European mythical bric-a-brac. Even King Arthur dies with a prophecy of later return.
I was a mythology geek when I was a kid, devouring books about Hercules and the Knights of the Round Table. The Bible, on the other hand, was something for people who were forced to go to church on Sunday. If I had been forced to make a comparison between the Narnia books and what I knew of religion, I would never have drawn the conclusion that it was a Christian allegory. This is what happens when you're a second-generation atheist.
One final note: The Lion, The Witch and The Wardrobe is probably the closest Biblical allegory except for The Last Battle, which tells the story of the end of Narnia. The books in between are mostly simple quest and adventure stories, with children set on their way by Aslan, but aided considerably less. I always liked those books better, especially The Silver Chair, The Horse and His Boy and The Voyage of the Dawn Treader. The first and last books left me a bit bored, and The Last Battle I actually found confusing, unsatisfying, and a bit depressing.