Describe Him: God

When we say that He is God, we declare several presuppositions to be true:
He is Deity. 
He is the only God.
He is the only true God.
As God, He deserves all worship and glory.

Conversely, in saying that God is God, we state that
we are not gods,
there are no other gods,
anyone else who claims to be god is a false god,
and no one else should receive the worship and glory that is given to God. 

Declaring God to be God reminds us that He is over us in power and authority.  In turn, we answer to Him. This demands obedience and consequences when there is a lack of obedience. In other words, man sins and God's holy character demands that sin be punished.

This leads to man's need for the Gospel, which Satan hates with a passion.  If Satan can convince man that there is no God or a different kind of god than the One revealed in the Bible, he drives man away from the Gospel and eternal life.  
But no matter Satan’s lies, no matter what an individual believes, the truth doesn’t change: God is God, the one true God.   And one day all will bow to worship Him.