Yes, but I think it fair to say that he didn't write "Creatures of Light and Darkness" with the objective of convincing some of his readers to worship Ra; whereas in the case of Lewis, it seems painfully obvious that he is trying to inculcate Christian values in his young readers. While I certainly don't have a problem with that as such, I think that in this case it sometimes gets in the way of telling a good story.
There are certainly fantasy authors who use explicit Christian theology in their work without any attempts at proselytization. Just as a for instance: "Her Majesty's Wizard", by Christopher Stasheff.
Why should a Christian World View somehow seem “odd” to the sci-fi-fantasy genre?
I think it's safe to say that when it comes to incorporating religious themes into sf/fantasy, most authors treat Christianity as Just Another Religion, albeit one with enormous cultural influence. For a writer to explicitly put Christian themes into his/her work with the objective of converting the reader is extraordinarily rare. I can't think of a mainstream sf/fantasy author beyond Lewis who does so (I wouldn't count Tolkien; his work is far more subtle than Lewis' when it comes to incorporating morality).
When Zelazhney wrote his fantasies, he did not “Proselytize” because he wrote from a position of non-belief. he drew upon The Myths of the past as cultural and artistic material.
C. S. Lewis, on the other hand, believed in the world view that he inserted into Narnia. Since he believed in the Truth as he saw it, then OF COURSE it will become part of his narrative.
Most of us here on FR believe in (at least) the principles of conservatism, Constitutional Freedoms, and free enterprise. It is therefore the NORM to see posts that are about THOSE things that we believe in. And we hope that what we write will convince others to believe what we believe is the truth.
Are we to censor the particular genre of Sci-fi-fantasy if it doesn’t conform to a pre-set norm of atheism, adherence to hard-science only, or the cultural trappings of ANYTHING but Christianity? This would fly in the face of everything we hold dear as conservatives and patriots.
Let C.S. Lewis share his faith in the the medium of his fantasy fiction. it is his inalienable right.
It is also your inalienable right to dislike it! :-)
But, be advised, my FRiend...Christianity (and Judaism) are rapidly becoming the target of persecution in the obamanation. Let us not join the chorus of abuse of the Christian World View by calling it “Proselytizing” as if that is a dirty word.