When God came upon earth he would have to identify himself as such. Jesus identified himself with God and as being one with God he also claimed that to see him was to see God.
In order to be God, Jesus had to be God like in his moral attributes, love and goodness and to be able to have supreme power and knowledge and to be able to demonstrate this. This was demonstrated by Jesus. Jesus claimed to be in Heaven, that the dead would respond to him and that nature would obey him.
When Jesus was born in Bethlehem he was born to normal parents. He immediately stood out from other kids with the way he gained knowledge and wisdom. Jesus' journey through his early years clearly showed that he was not just a mere person like others. His love and compassion for people and his understanding of all situations also proved his deity.
"There is only one God, and one Mediator between God and man, the man Jesus Christ". (1 Timothy; 2:5). The prior statement brings Jesus into a position of total superiority.
In my mind you have to believe in Jesus as a man-God or the bible and a big part of its messages doesn't make sense. When Jesus died on the Cross at Calvary is without a doubt the single greatest event for mankind. Throughout the Bible their are numerous accounts of Jesus as a man but also as a God. Jesus lived his life like other men in regards to eating, sleeping, tiring and was even emotional at times. My favorite passage is when God says to Moses, "I am that I am" (Exodus 3;14).
Jesus was both God and Man is proven by his ability to do Godly things and be man-like while doing them. To separate God and Jesus Christ is not possible besides the fact that Jesus done things in a human form.
Jesus had to become incarnated to save humanity because man had made such a mess out of saving themselves. All different kinds of sin were