Sacred Haven of Debauchery

Age of Empires with the The Rise of Rome expansion - 16 factions
Cossacks: European Wars with the Last Argument of Kings expansion - 18 nations

These are nations, and they differ not drastically. Some have access to certain technologies, others to different ones, but there is a general standard for all, and that is normal.

Warlords - Battlecry III - 18 factions

A rare piece of garbage, exactly what I was talking about, a perfect example for my thesis about the idiocy of more factions and it will be cool.