Mr_Crispy posted... I think they're supposed to be like the Titans in Greek mythology, precursor gods that got their asses kicked by the current gods. They just used 'ogre' instead of 'titan' because Queen.
Also the final boss in the first game was manipulating the war to try to revive one.
Yeah - the name doesn't really mean that much. The director, Yasumi Matsuno, just picked "Ogre Battle" and "March of the Black Queen" because he really liked the band Queen and thought it would be cool to name his game after two of their songs.