are they the same deity, just with different names from different cultures or are they two different gods

and yes i know Auri-El is Elven, and Akatosh is human

Well, Skyrim says Akatosh has always been and is something different all together and that Alduin is his son. Prior to that, Akatosh/Alduin/Auri-el were three different personality of the same God, different interpretations of the same God if you will but given a life of their own through mythopia.

edit: clarification, that's at least the most widely accepted theory at least.

Double threat: http://www.gamesas.com/topic/1400539-is-alduin-akatosh-or-his-son/

Alduin is the son of Akatosh, who has always existed, but Alduin and Auriel were Akatosh before he always existed.

Maybe.