My friends and I wanted to play Civilization: Revolution together. They both have Xbox 360s and only I have a computer.
We were wondering if it would be possible for us to play together, without me having to purchase an Xbox?
Even if there were, it is fairly rare that PC and Xbox 360 players can play multiplayer together. I can think of perhaps a handful of games where this is the case.
So the answer is no, you can't play Civilization 5 between a PC and the Xbox 360.