The other day I happened to see on television the beginning of the third Narnia film, The Voyage of the Dawn Treader, and found myself puzzling over what it is I don't like about these stories.
I normally like good children's stories and some fantasy stories, so I don't have a problem with the genre. Indeed, I rather like the sense-of-wonder aspect of suddenly travelling to a magical world through the back of a wardrobe (or the other methods used in later books). The problem is that I don't really like Lewis's stories.
I first read The Lion, the Witch, and the Wardrobe in childhood. When I read it as an adult in 1999, I commented that the children are less convincing than (say) Arthur Ransome's or Rudyard Kipling's, and seem more quaintly old-fashioned, even though the book is relatively recent, dating from 1950. I think Ransome and Kipling were drawing on vivid memories of their own childhoods, whereas Lewis seems to be looking at children only from an adult's point of view.
In 2008 I saw the film of The Lion, the Witch, and the Wardrobe on television, dubbed into Spanish, and then read the book again (in English!). I commented that the film was well made, but found it hard to think of anything about the story that I actually enjoyed.
My feeling is that these are stories written by a man trying and failing to remember what it was like to be a child. They come over as childish stories, and not in a good sense.
I really dislike the way most of the children outgrow Narnia by the end of the series, and Susan discards it as a childhood fantasy. How could anyone live through all that and then manage to suppress it all? I point out that, on their first visit, the children lived well into adulthood in Narnia: for fifteen years according to Wikipedia, though I don't find that specific figure mentioned in the book. You can't just dismiss fifteen years of your life as a childhood fantasy. If they didn't outgrow it then, why later?
Incidentally, having grown into adulthood as kings and queens in Narnia, they would surely have had massive problems trying to readjust to life as children in England. If I were thrown back into my schooldays from adulthood (even without having been Narnian royalty), I don't think I could tolerate going through all that again. As an ex-adult, I'd be a Problem Child with capital letters.
The only way to account for it would be if their memories of life in Narnia were mostly obliterated on return to England, as happens with dreams; and yet they do seem to remember at least to some extent. I don't think Lewis explained this adequately; and it strikes me as a bit of a cheat anyway. What happened to them wasn't a dream, and it lasted much longer than any dream.
Kipling, in Puck of Pook's Hill, used magic to make his children forget their adventures completely. Rather a shame, but at least he explained it explicitly, and it avoided any complications.
There are other problems with the stories that others have commented on, but I won't bother here.
If I liked the rest of it, I could probably tolerate the obvious parallel between Aslan and Jesus Christ, but I find it somewhat irritating. This is a fantasy story about Narnia: I don't want to find this kind of contrived analogy woven into it.
I read Prince Caspian for the first time recently, out of curiosity, and found it amiable enough, but a very slight novel with nothing much to it. In the end, the bad king's forces are defeated by Aslan, and nothing else that happens really matters. The Pevensie children are supposed to be important, but in fact their contribution to the plot is negligible. Lewis seems to have been a curiously amateurish novelist who was more interested in Christian fables than in telling good stories.
I like Tolkien better than Lewis, but even Tolkien, when writing The Hobbit for children, had a slightly patronizing tone that I find irritating. Fortunately, Tolkien didn't attempt to write about children (all of his characters are adults), and by the time of The Lord of the Rings he wasn't even writing for children any more: it's a book for and about adults. It's not unsuitable for children, but it's not aimed at them.
Some people may regard the hobbits as child figures because they're physically small; but Bilbo is 50 years old at the start of The Hobbit. Frodo is 33 when we first meet him in The Lord of the Rings, but he's 50 by the time the real story starts.