HEY! BLACK FLAG'S AI WAS ACTUALLY DECENT, YOUR CREW WOULD ACTUALLY DO stuff!
As for the other games, i'm not sure because honestly i enjoyed 2 as an assassin's creed game and 4 as a pirate game more than a creed game. 2 expanded on so much and 4 just gave us a completely different game. two flavors for two different people. 3 is the unwanted middle child.