I will comment on the languages not mentioned so far.
Wu Zetian's Chinese is definitely not befitting of royalty, very plain, like she's a commoner. It would be awesome if she spoke the Mandarin dialect of Xian. Plus a reconstruction of Middle Chinese has been done by scholars before, I guess they wanted Mandarin speakers to understand the dialogue, but it is so simple.
I sent youtube clips of Gajah Mada to my faculty advisor (he did work in Java, and knows Javanese as well as Indonesian), his short reply was "it's fractured Javanese, sort of". Make of that if you will.
Dido is speaking Phoenician, although perhaps with some Hebrew words.
Askia is speaking Zarma, a Songhai language.
Shaka is speaking Zulu.
Haile Selassie is speaking Amharic.
Nebuchadnezzar and Ashurbanipal are speaking Akkadian, though they should have probably spoken Aramaic.
Kamehameha is speaking Hawaiian (his voice actor is a scholar on the Hawaiian language)
Pocatello is speaking Shoshone.
Hiawatha is speaking Mohawk.
Montezuma is speaking Nahuatl, a modern version with Spanish loanwords.
Pacal is speaking Yucatec Maya.
Pachacuti is speaking Quechua, apparently Ecuadorian, with Spanish loanwords (Imperio Inca

)