This is one of so many questions we ask in our life.
I want to find out more, so I have asked few friends to get the idea or probably the foundation before searching through the internet to found out about it.
Some of friends would say, its because God loves us (i believe it was based on the John 3:16),
some say because we got to eat all those animal and vegetable (based on genesis, the creation)
Another will say, we were created to show His existence and to glory Him. Mention in from Paul’s letter to corinthian.
I was still not fill with it. I dont buy as feel, it is more than that.
I found something, when john piper mention it on their daily devotional video (desiring god). He created us for His glory and he said, you can find it in this verse.
everyone who is called by my name,
whom I created for my glory,
whom I formed and made.
Isaiah 40:7 (ESV)
And also some article they wrote. An article published on 2012, you can read it here. (https://www.desiringgod.org/messages/god-is-most-glorified-in-us-when-we-are-most-satisfied-in-him)
It says in short about it
Why did God create the world? And I answered: God created this world for the praise of the glory of his grace displayed supremely in the death of Jesus. The problem is that at the heart of that answer is God’s self-promotion. God created the world for his own praise — for his own glory.
So people see this as a problem — that God created the world for his own praise. They think such self-exaltation would be immoral and loveless. That may be how you feel.
God is most glorified in you when you are most satisfied in him. That’s the shortest summary of what we mean by Christian Hedonism. If that is true, then there is no conflict between your greatest exhilaration and God’s greatest glorification.
Chimi Kyo 