God is self-sufficient. We do not exist because God was desperate and needed relief from His lonely pity party or because He was depressed. He is not Macaulay Culkin in a “Home Alone” movie. Philosopher and theologian Jonathan Edwards in his book, The End for Which God Created the World, stated, “An emanation of his own infinite fullness was what excited him to create the world.” In other words we are the result of His goodness and greatness which “overflowed”. You and I and the world are a manifestation of God’s overflowing goodness. That’s part of the answer . . .  

In the Bible, we see the dominant theme of “God’s glory.” Basically God’s glory is his moral beauty and perfection. It’s an expression of his worthy nature. God created us to bear and reflect his moral beauty and perfection (Genesis 1:27 ). He created the world to display his goodness and his moral beauty and perfection. His moral beauty and perfection are evident in nature (Psalm 19:1-4 ; Job 38:1 - 39:30 and Romans 1:18 -21). All that He creates reflects his glory and honors Him as the creator and the one worthy of honor. We are created to reflect God and his overflowing goodness. We exist for his good pleasure. For some reason He thought it best to create us to add to his wonderful creation the universe.

Secondly, we were also created to receive Him so that we can reflect Him and his glory (or his moral and perfect beauty) like the moon reflecting the brilliance and beauty of the sun to the world. God desires a relationship with us, his creatures. Unlike the fatherless children of our days, the Lord desires to be in a relationship with us where we recognize him as our only hope and help (Romans 15:4). This is not out of a sense that God needs us to want him but rather He knows we will “self-destruct” without Him and will face death, utter destruction, and hell. His love for us is not out of his ego. In his love for us, He provides Himself because He knows that He is the very thing we need (John 4:14 ; Jeremiah 24:7). Basically the Father, (who defines perfection) wants the best for us. Lastly, because there isn’t one thing that’s better than God the creator, He gives Himself to us in a relationship through his son Jesus.

The bottom line?
God created us (1) to reflect His wonderful nature and (2) to receive Him, the very thing we need. It’s like God giving his blood at a blood drive because he (1) wants people to know that He is good, perfect, and just and (2)  knows it’s the very thing we need.