Without going too far off-topic (what was the topic?), I should note that this point has been answered:You know of their different cultures, but what about the masses? Look at it from a marketing standpoint. I think that most would look at it and say "oh look, a Shogun 2 copy."
As for the others, yes, they are fantastic time periods, but how many people would buy a game based around the Persian wars? I doubt most even know what they were. The past TW games however, have been easily recognized by the average joe.
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