Let's look at something a little different. What role does religion play in speculative fiction? It's an interesting question that depends on the scope of the definition of religion.
One of my recent reads was Robert J. Sawyer's Calculating God. In this novel, we learn that there are two alien races in Earth's neighborhood and roughly the same technological level of Earth. The two alien races have compelling evidence that the universe was designed by God. They think Earth's religions are silly.
Going back a few years (and taxing my memory), look at Philip Jose Farmer's Father to the Stars. This is the story of a clergyman on an interstellar voyage.
Religion is an integral part of human society, and it will likely be in the future, too. Some writers recognize this, others seem to ignore it. Granted, some stories don't need religion. My own first novel contains few if any references. It's a near future story that relies largely on the readers' experience of the world. On the other hand, in my "Stars" universe religion plays a major role in the lives of one alien race.
When you are creating a new world, using religion can help develop a rich and colorful world.
Look at Robert L. Forward's Dragon's Egg. We follow the development of the cheela, a race that lives on the surface of a neutron star. (Cool concept, but off topic.) We get to watch a religion form, evolve, and die. It adds considerable flavor to the story, and makes the cheela more real to us.
This is a totally different use of religion from the Christian Fiction genre, where religion is the point of the story. In SF and fantasy, it's best used as one dimension of a multi-dimensional story. At its best, this dimension can give the reader food for thought, but the writer needs to respect the reader, too. Nothing will turn off a spec fic reader faster that preaching.