When considering a new Civ to be added, ask yourself:
Can you really compare them to the
.) Maya
.) Babylonians
.) Ancient Greeks
.) Romans
.) to some extent, any of the others?
While there are some Civs i dont agree with in CiV4, they have mostly one thing in common: They did something amazingly.
Whether this was amazingly stupid (Mansa, im looking in your direction here), or something amazingly brilliant is not the point.
If that, which theyre renown for, is true or not: not the point.
They are known, by people around the world, for something.
Everyone knows the Germans, for events taking place mid-20th-century.
But they are known.
Everyone knows the Greeks, for inventing philosophy and buttsecks.
But they are known.
Everyone knows the Actecs, for nothing more than having existed at some point.
But they are known.
Like Paris Hilton, Civ just need to be known, no matter what for.
There is no "bad PR", only PR and better PR.
What has that Civ-to-be in question done to change the history of the world?
Have they developed a culture of their own, which influenced many others in many ways?
Have they conquered large amounts of terretory to form an incredibly large empire?
Have they developed an economy so splendid to outshine all others?
Have they built cities or buildings or monuments so vast and grand that no one thought it possible?
Have they brought forth an individual so extraordinary, that he is known to people from one end of the world to the other?
Have they provided incredibly important scientific breakttroughs, which still form a basis for todays scientists?
Have they accomplished a single feat that will be talked about in a 1000 years?
If you cannot answer at least ONE question with yes, then theyre plain unfit to be a Civ (tm).