I think this is one of the most powerful quotes ever on the topic of the existence of the supernatural. Getting someone to reason why we should believe that the existence of their β imaginary, invisible, purple fire breathing dragon in their garage β is more real than any one of the other imaginary dragons is going to involve lots of intellectual gymnastics resulting in nothing but a head injury.
Here is a fairly comprehensive list of gods other than one of the current favourites, that would need to be explained away as unbelievable in order to narrow it down to just one!