The thing about CS Lewis, is that he wrote the Narnia books a long time ago. He was best friends with Tolkien and encouraged Tolkien to write Lord of the Rings so any LOTR fans out there owe him your allegiance!
But more importantly, you have to recognise that social circumstances change over the years and demands increase for excitement. In an age when there had been World Wars, any margin of fantasy was welcomed by kids as there wasn't much adventure or fantasy books available at the time. Today is a different story.
When I was a kid, I liked the Lion, the Witch and the Wardrobe the best out of the Narnia books. The rest of them didn't have the same feel and I was disappointed with them.
I think the film will be good although it has already been dubbed the Mini Rings even though the LWW came first.
Interesting fact about CS Lewis:
He died the same day that JFK was shot in 1963 and no-one even noticed!
I think that's really tragic as in his day I'm sure he was really rated as an author.