When asking the question you have to have something with which to compare it. Christian civilization is superior to what? The next question involves a value judgment in trying to determine what makes something superior. I assume that superior means something which is held to be a good thing. Who decides what is good? For instance, the goal of Nazi Germany was to produce a superior human being and a superior society. Germany, Austria, and Italy were all considered to be Christian cultures, and many theologians supported the Nazi ideology of a superior man. I would also question if there is such a thing as a Christian society. There are Christians within a society, but does that make it a Christian society? Do Christians agree on what values within a particular culture should be promoted? There are too many philosophical questions that have to be asked and answered before we can declare that a Christian society is superior to something?
Christianity is the best plan we humans ever have discovered for fullfilling our intrinsic needs - a belief rhyming well with our inner nature.
The Old Testament is the basics, but what is revolutionary and true about the other one?
It is the Christian notion of “Agape” - the idea of the Universe being conceived in heavenly love.
Which is not any sort of love.
The love the Bible speaks of is one that holds the Universe together and directs Man towards the ultimate of his goals:
True freedom.
A core of Christianity is this:
Man has freedom, unlike animals, because God's utmost expression of love for his creation is Man. Man is created as an image of God “Imago Dei” - in the face of God (in Latin) - meaning Man is to be seen as the gardener of a paradise created by God.
Pico della Mirandola clarified this cornerstone of Christian faith in a beautiful fashion and from his interpretation of scripture Man has found the inspiration and courage of climbing to peaks unknown to his age.