If you read any creation story, you will notice that the Divinity is concerned with a very small realm. The focus of the Divine manifestation remains on Earth, which does not even count for a sizable portion of our solar system. Even if G-d puts a little bit of focus on the luminaries in the sky, the huge unexplored realms of the expanding universe are ignored.
Some might say that G-d is very clearly a human invention, because if His infinite knowledge of the universe truly did exist in his various holy messages, a non-human or non-earthly focus would be developed. Authors like Richard Dawkins are ready to say that G-d’s obsession with mankind indicates that any other human-like race in the great beyond would disqualify G-d’s existence.
Not often mentioned by atheist apologetics is the notion that the existence of other humanoid races never did disqualify the existence of a divinity. The Japanese and Norse mythologies possess many races of human intelligence—never are they used to annul the divinity—only to strengthen it, because they aid certain aspects of the pantheon or divine being.
Even the Bible has hints of other races for the purpose of creating a shared world not entirely controlled by humans. The “Anakim” and the “Nephilim”, commonly translated as “giants” or “fallen ones”, are two examples.
Clearly, the humans were the most powerful, and the focus, but would the Greek gods be any more or less powerful if centaurs did not exist?
The end of the matter is: no matter what god you choose, other races aside from humanity can exist. Even if these races did not exist, they serve as a pointer that if other humanoid races are discovered anywhere else, they can get along with humanity, recognize the same god and, perhaps most importantly, not disqualify the Divinity’s existence.
Another important concept to realize in exploring the great frontier of space is that there was a transition that took place with G-d that occurred when the human frontier on earth was expanding. Should we encounter another alien race out there, this process will happen again.
G-d was originally the G-d of just the nation of Israel before He became the G-d of all else in the world. After more of the world was explored, G-d became the Lord of all the Earth. This did not disqualify his omnipotence, though—He is capable of limiting Himself or “hiding His face” if the occasion calls for it. (Always being there can create an unhealthy relationship with your beloved, even if you are G-d)
Another transition is occurring right now—G-d, previously the Lord of all the Earth and environs, is becoming the G-d of the whole universe and all that it holds, whether or not we know what is there.