I'd say that to be an actual Christian you would have to believe in God, because the Christian doctrine repeatedly states that you must believe in Him as the Son of God. By definition if you don't believe in God you are not a Christian. HOWEVER you can follow the teachings of Christ(minus the whole "Whosoever believeth in me" part) and share values with Jesus, but then you could just be Buddhist and not realize it.
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson