Gah I don't understand why thus is such a hard thing to understand in Christianity. There were and are other gods. Some of them tried to set up shop here... some of them will in the future. There is only one God of gods, and therefore that makes the Most High the one True God.
Not to mention, god/elohim is a magistrate. The first commandment is like a King saying, "I know there are princes, princesses, centurians, guards and elders, but I am your only King, and no one else (prince, gaurd, etc.) Is King before Me."
On the OP note, I think salvation is unique to humans. We were supposed to be (and will be) THE rulers and dominion holders of this planet, and physical analogues of the Kingdom of Heaven. The philosophy that the entire planet turned toxic/dangerous/poisonous after Adam lost perfection makes perfect sense: imagine the loss of respect angels would have of God sinned. So, it would seem that, like God, our perfection, or lack there of is directly related to the progress and well being of the entire physical creation... just like God's perfection sustains everything.
And, no god is required to do anything for its creation.