The questions we must first ask in relation to our question:
Is there equal evidence for fairy tales as there is for God?
What can we discern from the actions of those who follow such beliefs?
Is simply wanting to believe enough to truly believe?
Atheists argue that a belief in God is no different from a belief in something supernatural, such as Bigfoot or Santa Claus. If both are simply stories passed between generations with no evidence, how can they be different?
Psalm 19:1 tells us:
The heavens declare the glory of God, and the sky above proclaims his handiwork
Our universe, animals, and the human body all point to an intelligent designer who is all powerful, all knowing, and always present (see The Teleological Argument). The evidence that such a being does exist is displayed not only through this but also through the many things that are unaccounted for in an atheistic worldview—objective morals, consciousness, and miracles, to name a few.
Another difference between those who believe in God and those who believe in fairy tales is in the testimony and actions of those who believe in God. History, scripture, and tradition corroborate that all but one of Jesus’ disciples were murdered for their faith. These deaths are said to have included being crucified upside down, being beheaded, and being flayed alive. It therefore must be asked: if God were just a fairy tale, why would the disciples be willing to be subject to immense torture to defend a lie?
One could argue that if you wanted to, you could believe whatever you wanted to believe. To some extent, this is correct; however, the difference between genuine belief and false belief is in how we are convicted.
For example, one could work to falsely believe that Santa Claus is real, yet their conviction of truth is never going to be in favour of his existence—it will always lean towards knowing him to be false. A belief in God, however, does the opposite. At all times, as a Christian, our knowledge of God's existence compels us to act in accordance with His will, and any deviation from that brings resounding guilt to the believer.
Conclusion
A belief in fantasy beings or fairy tales is maintained through the restraint of evidence and logical principles. Belief in religion is born through the conclusions drawn from evaluating the evidence presented and having faith in what has occurred.