Why did Jesus need to to be born in human flesh?
ESV - 14 And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
I believe the question needs to be reworded because Jesus was not born in the image of man but as man. All the above explanations have correctly answered the real question which is 'Why was Jesus born as man'.
The term 'image' refers to God's creation of us in His image (Genesis 27). That refers to the soul that we all possess and not to our physical human form. That is why Jesus spent His time correcting our inner thoughts and desires and not our external physical image - The Beatitudes (Matthew 5-7) for example.