Historically Jesus was really here so Jesus was not "invented."

Also, like I said in other posts, the one thing that differentiates Christianity from other religions is that the other ones required salvation to be earned by our own merit.  Christianity is not about what we can do to earn our way to heaven, it is about what God already did and our response to that.  Do we accept or reject?  It is really that simple.  Of course, in accepting Jesus our lives do change.  He changes us from the inside out.  Instead of hate he puts love in our hearts as we let Him change us and we have more compassion on others and so on.