Merriam-Webster's online dictionary defines "myth" as -
1 a: a usually traditional story of ostensibly historical events that serves to unfold part of the world view of a people or explain a practice, belief, or natural phenomenon b: parable, allegory
2 a: a popular belief or tradition that has grown up around something or someone; especially : one embodying the ideals and institutions of a society or segment of society <seduced by the American myth of individualism — Orde Coombs> b: an unfounded or false notion

"Fairy tale" is defined as -
1 a: a story (as for children) involving fantastic forces and beings (as fairies, wizards, and goblins) —called also fairy story b: a story in which improbable events lead to a happy ending
2: a made-up story usually designed to mislead

And it defines "mythos"
2: a pattern of beliefs expressing often symbolically the characteristic or prevalent attitudes in a group or culture

It seems to me that Alex is right: religion cannot really be considered a fairy tale. It's more in line with a mythos.
I think you can make a point of defining the stories in the Bible, for example, as myth. Possibly even fairy tales in some cases.