Wow, what a give away! Nice!
Interesting, I was playing Civ III just before came here. I don´t have a favorite one, but love all the ancient civs from Mesophotamy region. (like Babylon, Sumerians, Phoenicians). But if I would appoint one, I´d say the Achaemenid empire (or the first Persian empire - about 550 BC). Besides being an empire (what implies conquists, lots of wars and blood), I really admire Cyrus heir. They used to respect the others cultures which were "conquered", making a rich and diversity cultural empire. Just for know: most people believe that the Roman empire was the "biggest" (well, its easy understand it because much from the called east culture, in many aspects such as law and military enviroment, came from there). But the Persian empire (they used to call themselves as Iran or Achaemenid) was the biggest one (cultural, military, territorial and commercial)