But you do exist. And your god doesn't exist. So you're back to square one, how would you be able to know that your god doesn't exist?
lets get this sorted out for once and for all.
If there is a God, I would expect him to reveal himself to me, or to talk to me.
Now lets leave personal experience out of the equation and take what I learned from the Bible.
God did walk with His creation in a paradise of an earth in the beginning, but Man lost his inocence, and became corrupt and was removed from God, for God can not be in the presence of sin and corruption.
Not because there is something short of the omnipotence of God, but because corrupt man will simply die in the face of God's full glory.
Therefore, we can not be in God's presence anymore, we will burn up and die!
Then God visited his creation in the form of an Angel, where the angelic body contained the Word, or Jesus.
This angel appeared to Moses, Abraham and many other.
God eventually appeared in full glory to Moses, but He had to protect Moses and covered him with His hand.
God also appeared to Israel, but they told God not to speak to them directly, for they were terrified of His light and voice.
Then God made the rule of speaking through a prophet.
The above is a very logical explanation of how God actually interacted with His creation, but we rejected Him in this act.
Then God came to his creation in the shape on a normal man, proving that he is God with miracles, and prophecies, which was by the way immediately recognised by the priests.
Now, they hated Jesus for informing them of the things they were guilty off. They just could not BS Him.
Now, if I were to live with a closed mind, I will reject all these claims from the Bible.
But, If I were to think about it in a critical manner, I will have to conclude.
If I was God, I would have done the same.
Therefore, you want to know how one can prove the existance of God.
Easy, Just remember that He even came to Earth as a Man to be with you and to save you from eternal corruption.
What more do you want.
I have a God who made it all, walked with us, was rejected by us, who came to me as a man, who was killed for doing so, who now returned to heaven, and reveals himself through His Spirit and intellect.
The choice is yours!
Accept this, or reject it all.