Read carefully, Valkyrie. What Lewis is stating is that he intended to write no allegory (a specific style of literature, e.g. Pilgrim's Progress), and that he intended no moral or message. That is not the same as saying that Aslan was not a Christ figure; in fact, at the end of Dawn Treader, Aslan comes out and admits that He is Christ, and that Lucy and Edmund are not being allowed to return to Narnia because it is their time to learn to know Him by His name in our world.
There's much confusion over this point, and it seems to me that it centers around two points. The first is most modern people's misunderstanding of the term allegory. Many moderns refer to any story with a message or meaning as an "allegory". This is not true; an allegory is a very specific style of such story, such as the aforementioned Pilgrim's Progress or Dante's Inferno. There are plenty of stories with meaning that are not allegories; Lewis' The Great Divorce would be an example of such.
The other point of confusion lies in the misapprehension that if there is meaning in a story, the author must have set out to put it there; i.e. to write a "morality tale". Speaking as an author, I can tell you that this is untrue. I have written stories just to write stories, only to have someone come up later and say, "Wow, that was a tremendous message in that story!" My response is "what message?" Lewis experienced the same phenomena, as did Tolkien: neither set out to embed a message in their stories, but the message crept in nevertheless.
Now, if you're an anthropocentric thinker, the question is settled by the issue of what the author intended. If no message was intended, then there's no message, period. But if you're not an anthropocentric thinker, and admit that there can be greater forces at work than just one man's thought and imagination, then the possibility exists that the message ended up in the story not because of the author's will, but because of the intentions of Someone Else. Lewis and Tolkien (and I) are not anthropocentric thinkers; in fact, Lewis admitted that his experience of writing Narnia was that a great golden Lion kept leaping into the picture and demanding a place in the story. If you think like Lewis, or have even written a story and had one of your characters "run away with it", then you can understand how a story can have a meaning that you never intended - but perhaps Someone did.