CTM said:
Atheism isn't a religion. I'm sick of people who think it is, too.
Hmm. Somebody better alert the US Supreme Court. They have, on numerous occasions, "recognized" athiesm as a religion (albiet by inclusion as they have lumped it in with other religions against which discrimination is unlawful).
I may be overstepping by bounds here, but I think the reason Firaxis decided to expand the role of religion in the game was because it WAS a driving force behinds most major civilizations and what they did. As for why some were excluded and some included, I can only guess but here are my 2gpt:
[WARNING: THIS IS NOT INTENDED TO BE OFFENSIVE TO ANYONE. IF WHAT I SAY DOES BRING OFFENSE, YOU HAVE MY DEEPEST APPOLOGIES]
Athiesm -- Let's start off with this one. Athiesm is not included. So what? How did athiesm contribute to any technological, cultural or geopolitical happenings of the last 6000+ years? Did anyone civilization set forth and declare "We do this in the name of, well, ourselves!" with any significance? The problem with athiesm is that it is an inactive and non-motivational belief system. Yes, some can make a strong argument that Humanism and Secularism are the banners behind which athiesm marches. But athiesm in and of itself, does not prosthelytize, does not inspire or demand action, does not hold meetings, does not congregate (ok, with the possible exception of the entertainment industry

j/k), and has only been the "official state religion" of one relatively new and, for the most part, unsuccessful form of government. So what has athiesm done for us lately? Or at all?
Judaism -- Why should it be in? Well, for one thing, it has what no other religion popular around the same time of its inception has: Staying Power. This religion, practiced by (as someone said) no more than 50 million people at one time has been around since before there was even written language and it still exists. It is hated and reviled by more than one third of the religious world today and yet has withstood all attempts to irradicate the (in comparison) small number of people who worship it and who live in a (relative to the world) postage stamp sized nation in which its culture is based. What's more, this tiny nation with its paltry 50 million or fewer inhabitants is one of the major politial, financial, miltaristic and cultural players in the modern world. How you could have the religion of Judaism and not include the Jews as a playable Civ, however, is beyond me.
Zoroastrianism As stated earlier, a religion which, while lasting a millennia, had little significant or long lasting effect on civilizations of its time or those which came after. Yes, there is a constant ongoing debate as to whether Christianity got its ideas from Big Z or not. However, just because it was the state religion of the Civilization which brought us advanced mathematics is not, in my opinion enough to include it.
Polytheism I am against this as a catch-all category. I feel Animism would be better as a tip of the hat to the North and South American and African cultures who followed this belief system. While it goes against my earlier arguments of What did it directly or indirectly contribute, I think it is difficult to rationalize having Iroquois, Sioux, Cherokee, etc
, as playable Civs without also having their major religion. If, on the other hand, we are referencing the ancient Greeks, Romans, Egyptians, Scandinavians, et al, who held these beliefs, I would have to say that Hellenism would be the best choice as a collective term for the ancient philosophies and religions. In my opinion, the Greeks and their ancient religion and philosophers had more influence over their world at that time as well as on successive civilization up to and including the modern world than any other polytheistic faith.
Christianity and Islam Yes, they are new faiths, but together their practitioners make up more than half of the worlds population. The two combined have been the cause or inspiration of more cultural, political, economical, sociological, militaristic and political advancements, atrocities, influences, works and wars than any other religion (primarily in the western world).
So, what would my list be?
Judaism
Buddhism
Hellenism
Animism
Hinduism
Christianity
Islam
And include the Jews (or Hebrews) as a playable civ (King David, perhaps?)