What is one thing that God wants?
Bible speaks of many things that God desires - our obedience, faithfulness, sacrifices, love, praise, worship, etc. But is it possible to summarize all his desires in just one? This desire would then be the main purpose for which He created the world.
Reformed theology, which came out of Reformation and theology of John Calvin, and is now a foundation of Presbyterian church, provides the following answer:
1. God’s goal in all that he does is his glory, in the sense of displaying his moral excellence to his creatures and evoking their praise for what they see
2. Man’s goal in all his actions must be God’s glory in the sense of praise by word and deed.
3. God so made us that we find the duty of praise to be our supreme delight
This coinciding of duty with interest and devotion with fulfillment was classically formulated in the first answer of the Westminster Shorter Catechism: ‘Man’s chief end is to glorify God, and to enjoy him for ever.’
If you want to know more, read John Piper’s book “God’s Passion for His Glory“, which is basically a long preface by John Piper to a book by Jonathan Edwards “The End for which God created the world” (the Edward’s book is also included). You can also download the book for free (in pdf format) from www.desiringgod.org