That it feels like a living gameworld. Few MMORPGs have succeeded to create such a living world as FFXIV and I think that is in great part thanks to the story. To have to play through hours upon hours of story and getting to know many of the characters of the world really makes the player bound with the world and its inhabitans, other players included. FFXIV just feels more alive than its competitors on the market, and this is what i think makes it a winner in the long run.