Jesus is the most significant part of the Christian tradition. Just looking at the etymology, "Christian" means, "like Christ." The crux of Christianity is salvation through Jesus' death on the cross. Through His sacrifice, all those who believe in Him are able to have eternal life (John 3:16). Christianity MUST have Christ because without His death and resurrection 3 days later, the entire point of Christianity - salvation and eternal paradise in Heaven with God - doesn't exist either.

Christianity and Judaism are very similar except for when it comes to Christ. Those of the Jewish faith also believe that there is a Messiah who is coming to save them from eternal damnation, but that he has not come yet. They do not believe that Jesus was the Messiah, and that is the fundamental difference between Christianity and Judaism.