I don't know, and no one has any good arguments.
A god is not required to explain anything in the universe, so I just assume a god does not exist.
In the Cristian sense of god, god has no direct effect on the world, making the question meaningless.
It would be the same as believing there is an teapot in orbit between Uranus and Neptune, too small and dark to see with any telescope. I could say it exists, and no one would be able to disprove me, but that doesn't make it real.
Strangely enough, if instead of a teapot (which at least would be possible, if hugly impractical to find) you use an entity that is invisible, intangible, does not do anything else that could allow it to be detected (most omni-gods), then billions believe it.