True believers don't want to admit this because it makes them feel uncomfortable, but we know who created God:
Humans created God.
Unlike them, I have plenty of evidence to support my case. God has human attributes and limitations, such as emotions. He shows anger, compassion, hatred, love, jealousy, and regret. He is often described as having human physical features, like arms, feet, eyes, breath, and voice. He produced a human offspring, who was born of a human, and who physically resembles whichever culture believes in him. He communicates in human language and acts according to human wants and needs. He plays favorites among cultures or ethnic groups on Earth, protecting some while punishing others. He interacts and intervenes in human affairs, and is often referred to as a father figure. He is a character in a book written by humans, each with their own personal, social, and political agendas. In all these respects, he is very similar if not identical to the thousands of other deities humans have created throughout history.
God is not an omnitemporal, extraspatial, unknowable, or alien entity. God IS human. He is a reflection of the best and worst among us, our hopes and fears, and our potential to create or destroy. He is the explanation for everything we do not yet know, or are unwilling to accept. He serves whatever purpose we require, and changes as human cultures evolve.
Humans create the gods that create them in turn.