For starters, they all assume Jehovah exists, or seek to prove he exists. However, we have falsifications for most of the claims of Jehovah:
* Egyptology disproves the Exodus
* The Documentary Hypothesis disproves inspiration of the holy texts
* Quantum mechanics disproves omnipotence and omniscience
So the field of Christian philosophy is built upon sand which has already been washed away; the foundations already collapsed. How about the main philosophers?
* Aquinas just parroted Aristotle
* Augustine claimed that war can be justified and that souls exist
* Erasmus didn't really say anything of note
* Ockham gave us tools for breaking out of Christianity!
The main contribution of Christian philosophy to the rest of philosophy is the confirmation that Jehovah is an epistemic dead end.