The best reason to believe in a God is the probable existence of a God.
Depends on what probability and existence mean to you ... very deep metaphysical concepts (with probability ... the difference between the frequency definition and the Baysian definition ... with existence ... see a hundred philosophers).
I have no problem with godlings/demigods ... and admittedly, pantheism could imply an impersonal "ground of being" rather than a personal theism. But given my view of incarnation .. I am betting on personal theism, I would be very surprised if it works out differently.
If by probably existence, you mean empirical evidence for the monstrosity of Greco-Christian theology ... then I don't see that being probable at all. Dancing angels on a pin are more likely.