I fail to see where it having Chrisian elements to it should be an issue at all. I find it kind of ironic that when something similar to this comes along with a focus on non-Christian religion or philsophy, or that is critical of christianity and/or organized religion in general it's presented as a good thing, but here it's not. I don't think you have to be a believer to appreciate the messages or the analogies, and really I find something rather disturbing with the implication that there is something wrong with being a believer.
Someone whips out "The Matrix", or movies based on "Journey To The West" which is heavily religious (involving gods and the like), and I notice people don't feel the need to make quite the same issue of it. To be honest I actually thought "The Matrix" had just as many analogies as Narnia did in it's own way.
I'm not going to shoot off a list of movies here, or anything, I just don't see why this even needs to come up as a major talking point in regards to the movie.