In the second chapter of Engaging God's World Cornelius Plantinga Jr. goes over the creation of the Earth. Plantinga talks about the fact that even though Jesus Christ only came to Earth about 2000 years ago the Earth was created for him because he is eternal.
Later Dallas Willard points out that God is the most joyous being. We buy all sorts of material things to make us happy, but God already owns everything anyone could ever want even though he does not desire material goods.
Plantinga seems to think that the purpose of God creating everything that is not human is to give us something to ponder. Learning about God's creations can help us learn about God. Other creatures on Earth also give us some responsibility. God wants to see if we are responsible caretakers.
He also goes on to explain that we need to take time to be able to meet with God in our hearts. For if we cannot meet God in our hearts how are we going to meet him in the business of our daily lives. Prayer is a good way to communicate with God. Prayer gives God glory and helps in our spiritual life.