I think there is a broad and subtle territory in between, although Hollywood's ability to navigate such regions is a bit spotty. Certainly, the story is inherently religious, but so is The Lord of the Rings, and in many of the same ways — Lewis just made the Christian worldview much more explicit than Tolkien did. If the Narnia film tones the religious subtext down to the level of LotR, it should work pretty well.

My personal view on Narnia is subtle — for me, myth is a doorway to the sacred, without having to be true in the normal sense, and any story that touches me in the right way is fair game — a Jungian view, perhaps. Anyway, I think The Lion the Witch and the Wardrobe is a better instantiation of the archetypal story of Redemption through Sacrifice than what it's based on, and since it is neither alleged to have occurred in historical time nor encumbered with the same baggage, I'll take the opportunity for a sacred encounter with tha story, and then get back to being a Jewish pagan, or whatever else I was doing.

But that's me, and my quirky metareligion. Your mileage will of course vary.