God created us out of free and unselfish love. When a man loves, his heart overflows. He would like to share his joy with others. He gets this from his Creator. Although God is a mystery, we can still think about him in a human way and say: Out of the ‘surplus’ of his love he created us. He wanted to share his endless joy with us, who are creatures of his love.
From the Catholic Youth Catechism (question 2)