I think this one tops the last assassins and is the best one out of the series. The ship battles are really cool and it is fun to bounce around all of the islands. The graphics are amazing and the game sounds and effects are so realistic that it really seems like you're almost part of the game.
I gave AC: 10, AC2: 9, BH: 6, REV: 7, and AC3 a 9. Now this is back to a ten. The first couple chapters took the spirit away but it came right back as the story progresses. I won't ruin anything... but it makes sense why its seems bad when you see how you get your assassin's outfit.
Good: The graphics, environment, and gameplay with pre set abilities. (not to mention the tear jerking ending). The environment is beautiful and amazing no matter if you are in a cove, deep jungle, or the ocean. You can be a brutal fighter, assassin, or a pirate. You don't have to learn you basic skills over or earn your weapons like you did in most of the others. Your upgrades come with your hunting skills. The resource feature is great. You can spend many hours plundering the sea or just go through the basic gameplay. It avoids the "100 plus items collections" achievements too.
Bad: There isn't much to complain about unless you hate the Caribbean or Pirate theme in general. Its like how I didn't like Ezio too much.
Ugly: The only thing is that you can't judge your "Assassin" get go in this game. It drains your spirit as an Assassin at the start. Just let it take its course though, it makes sense.