Many Christians believe that the historical Jesus was not only a great realized man and spiritual teacher but that he was in fact, God, the creator of all. This belief seems to stem from the biblical quote attributed to Jesus: "I and the Father are One" (John 10:30). By "the father" it is believed Jesus was talking about God, although there are other interpretations.
A key point to make about this quote is that saying you are one with something or someone (is this case, God) is not the same as saying you are that thing. Instead, this oneness could refer to a shared purpose or mind-set such as saying "I am one with communism" or "I am one with Obama", for example.
If Jesus thought he was God he could simply have said "I am God". Instead he chose to say "I and the Father are one" which clearly reflects his sense of oneness with "the Father" rather than his claim that he was "The Father".
The idea that it is possible for the creator of the universe to be able to contain himself to one human body seems strange to me. Surely such a being would not fit into the small confines of a single human life. Also, if He did, what would his life as a man mean? For he could not serve as an example to mankind if he was of a different order and magnitude to the rest of us.
Only if Jesus was a man and not a God could his life be an example to the rest of us. If Jesus was not truly a man but God himself then what would his life mean? That God lowered himself to our level, to achieve what? Show us he cared? Forgive us of our sins? This interpretation makes no sense to me but I understand many do hold onto this view and it seems to mean something to them. But to me the idea of Jesus being a spiritual being, as we each are, and not the God of all, makes more sense and shows what's possible when we follow the universal spiritual path through to its conclusion. This is what makes Jesus a way-shower and the spiritual light of mankind, not him being some kind of super-natural being who condescended to our level for a short while.
See also: Was Jesus God? by Kim Michaels and friends.