Example 1 of Ageless Cyclical World: Our World. There are tons of creation myths in the world (for the purposes of this example, Big Bang is equally a myth as Judao-Christian's "In the Beginning..." as is Buddhism's "Om" [hope I referenced buddhism's creation story correctly]) but no one knows for sure which is correct. (For the record, I'm a christian and believe the christian version, but for purposes of RPG setting creation, I"m not going to put my own beliefs ahead of anyone else's.) In this world, there can be competing myths, each tied to a particular god or pantheon. Here, religion wouldn't be a question of "Do you worship god A or god B?" but more a question of "Do you worship my god/pantheon or no?" And as in our world, some would be passionate about their god and would want everyone to worship their god while others would be more respectful of another's beliefs.
Example 2 (for creation purposes only): The Dark Crystal/Castlemourn In The Dark Crystal, we know 1000 years before start of the movie, there was a powerful race that cracked the crystal, but we know of nothing before then. Aughra knows about what happened before then, and probably the Mystics/Skeksis know as well, but all others in the world don't appear to. In Castlemourn, there was a great and terrible change that happened a few hundred years ago and no one (even those old enough to have been alive back then) remembers what happened before then. A world using these as inspiration could simply be that the "actual" creation of the world is simply not addressed. Various religions and philosophies can claim to know the truth, but there is no "be all and end all" answer stated.
thoughts?