This is a tough question that I still don't fully understand the answer to. If you think about it, there is almost no purpose to our creation. And furthermore, to be called the crowning jewel of God's creation... I find it both humbling and ludicrous. Now, I know what you're thinking. "How could you say this?" Please don't take it wrong. I fully believe that God is real, all-powerful and all-loving, but why would you create something you know will ultimately fail you and break your heart?
Here's what I think.... I wouldn't! If I knew something would just disappoint me and let me down, I wouldn't create it. Good thing I'm not God huh? I'm far from perfect. I'm sinful and disgusting like the rest of God's children. Although, that's not even true because in Psalms it says we are "fearfully and wonderfully made."
However, as I think about it more, I really am a creator (notice the little "c"). Not only am I a writer, who loves to create new worlds in the stories I write, but God gave me the gift of pro-creation. When I marry the love of my life and fulfill His command of bearing children, then I will be doing the same thing God did in creating us in the first place.
I told someone once, "I connect with God in a different way when I write, because the characters in the story don't know what's going to happen to them. It just does. So I try to live my life like a character in a story God is writing." On top of that perspective on my writing, when I start a family, I will be creating something I will love dearly, knowing he/she will just let me down one day.
God gave us the ability, and blessing, to bear children and in our image, which is ultimately God's image. Ever notice (and I know you have) how much children look like their parents? It's a model of God's creation of man over and over again. He teaches everyone this lesson of how He created us in His image, and about our rebellion against him by having us go through what He did.
He lovingly created us, which is the answer to the question of why God created us. Love. I've also always found it interesting how it takes the greatest physical act of love to create the children we will love so much. It really teaches us God's love for us. Even though they let us down and rebel, in the end they truly love us back.
Which brings up another question to chew on for later. What about the children who rebel and never repent?