Different Salvation in the Four Gospels?

The skeptic writes:
The four Gospels, Matthew, Mark, Luke and John are regarded by Christians as historical accurate accounts of the life of Jesus. But what I'm about to show you will shock you, because there is a serious difference between them that the Church either doesn’t know about or won't tell you about, otherwise its Gospel theology would crumble to dust! What I am going to show you is that the first three Gospels - Matthew, Mark and Luke have a different Jesus and a different Salvation theology than the Gospel of John does. This logically indicates that the Salvation concept we have today, central to Christianity, evolved through mankind after Jesus supposedly left Earth. Therefore, it is a human concept, rather than a divine one, which is very bad news for fundamentalist churches that like to preach about sin, salvation, and redemption.