Destiny checks every requirement to be an MMO based on the definition of the genre. - Interact with millions of players, check - Game is hosted by a company check - RPG, check - Game evolves while offline, check Halo is not an MMO because the world is not persistent or online only. Let alone it is not an RPG. Again, here is this link. https://en.wikipedia.org/wiki/Massively_multiplayer_online_role-playing_game It is an MMO.