I believe everyone is agnostic. If there was the possibility of knowing for certain things would be completely different. Even people that say they know without a doubt that God does exist are only able to know to the extent that they can convince themselves and occasionally a few credulous others. There is no solid proof of existence, and non-existence can’t be proven.
Can you say you know for certain beyond all doubt that everything you listed does not exist on some realm/planet/dimension/ect? What about all the Greek, Roman, Norse, Hindu, and various other gods throughout history? The Egyptians actually had a crocodile God, Sobek, they worshiped him and even had crocodile hatcheries devoted to him. He was extremely real to the Egyptians that worked and traveled the Nile at the time, but we laugh it off as ridiculous now.
As of yet no one, at all, is able to prove beyond their own personal satisfaction that any God or gods exist. No one is able to completely disprove any type of existence. The only option available to anyone beyond their own personal view, which counts for essentially nothing in the scientific view, is that we can not know one way or another. That is that reason I chose to be Atheist. There is no reason for me to believe in any type of God because there is not the slightest bit of proof in favor of one.
As Richard Dawkins said when asked, if it is at all possible that some type of creator/deistic force/God of any kind could exist. He responded with (paraphrasing) it is possible that leprechauns exist. Any creature we can dream into fantasy could be real, but why would we possibly assert it to be real without the slightest bit of evidence?