Let me start by saying that I am not an AC franchise fanatic. I did play the original, which I thought was a very good game. After that, I didn't play 2 or 3. I could easily have played them as my family are gamers and we own them, they just didn't draw me in.
So, with the purchase of a new PS 4 (and an xbox one as well) we got AC 4 as one of the release titles. Let me start by saying this game is a swiss army knife of sorts. There are a LOT of activities to undertake in terms of gathering and completing challenges/activities. Early on it can be a bit daunting, but overall I found most of them fun and looked forward to participating. I also think, while a bit repetitive, the story line is enjoyable as you progress your way through it. I gave the game an 8 because there was a definite period of a couple days that I was thoroughly addicted to sailing the seas and accumulating the booty. Think Sid Meyer's "Pirates" with a more graphical interface. It's very satisfying to fight battles at sea while building your ship into a weapon of war.
I could not give it more than an 8 because at some point that feeling fades and the game turns more into an assignment of rote action, focusing on completing the huge number of outstanding tasks that remain on your "to do" list. Still, I would definitely recommend this game, even to people that may not be too caught up into the franchise itself.