While I have not completed every Assassin's Creed game, I have played portions of most (though I have not touched Origins or Odyssey). Black Flag is the greatest of them all. The Ezio trilogy may have the best story, but this has a fantastic balance of excellent gameplay and a decent story. If you are looking for the ultimate AC experience, go with Black Flag or Syndicate.
Review of Assassin's Creed IV: Black Flag
