Lets say this for the sake of making a discussion: You somehow find a genie that is willing to grant you one wish, but that wish must be related to making a superstitious belief true.
For example, I would choose reincarnation so long as it was only Human reincarnation. A person wouldn't be able to become an animal in a next life. Humanity would just continue recycling its own collective consciousness.
This is all for fun. Use your imagination. This is a "what-if" scenario. I don't expect that you actually endorse such silly ideas.
I would imagine some people wouldn't choose anything. I guess that is fine, but its not any fun. :p
If you step on a crack, it actually breaks your mother's back. Just kidding. :D