Originally Posted by Synamon
To be fair some like Narnia were fantasy rather than scifi (I tend to lump those into the same category which might be misleading). Others were probably just bad scifi that wrapped everything up with a bow using religion. The Ender's Game sequels would be an example of the religious theme eventually overpowering the scifi elements.
Well, Orson Scott Card's kind of notorious for a reason. And C.S. Lewis was IIRC a convert* who was deliberately writing faith-based allegory and parables.
I personally find overtly religious stuff in sf/fantasy/other speculative to be the exception, rather than the rule.
* I forget whether it was Tolkien who converted him from agnoticism to Christianity or the other way around.