I’ve contributed an abbreviated answer to this question as part of a symposium at Patheos:
http://www.patheos.com/Resources/Additional-Resources/Why-the-Incarnation-Matters?offset=1&max=1
Check out the site and chime in.
Here is the rather longer version of the answer I gave:
From the beginning Christians have affirmed that Jesus is both fully God and fully human.
Why?
If Jesus is just a good guy, then the world has one more hero — but nothing more — and we are stuck with no way out. You can stack up martyrs like firewood (and many have), but while the example may change the behavior of a few, the world remains a broken, hopeless place.
If God had not bothered to tell us that we are beloved by entering into our lives, then we would have been stuck with the architect of the cosmos, living at a comfortable, divine arm’s length from our chaos. Nicely celebrated at the opening of Congress and football games, but no earthly good.
The incarnation says “no!” to both alternatives and it is important precisely because it does. Its message is one of hope and deliverance. God is different enough to be capable of saving us — enough like us to understand our needs.
That is why from the beginning Christians have also affirmed that God is both transcendent and immanent: different from us, free of our frailties and, at the same time, like us, deeply aware of our struggles, attuned to our needs, in our skin.
Some have focused on a transcendent god. Think angry old man in the sky — perfect, judgmental, clear about what a mess we are.
Faced with a god like that others have argued for an immanent god — someone like us, becoming, emerging, struggling. Think, screwed up just like us, only in charge of the cosmos.
A god who is only transcendent is incapable of loving us. A god who is just like us may care, but is incapable of delivering us.
A god who is both transcendent and immanent is the only kind of God who can help us: different enough to be capable of saving us — enough like us to understand our needs. Both are necessary to the Christian message.
Jesus is Emmanuel — God with us.
I’ve always wondered about those who excuse behavior with the phrase, “He’s only human after all!” We’ve forgotten or neglected the most important part of being human. Having a close relationship with our creator, and letting God be God. Jesus wasn’t fully human by accident. His life and behavior is meant to be the model for all of us. We should scrap the (“He’s only human after all.”), and substitute “If only he were human.”