Assassin's Creed 2 was going to be my GOTY 2009, until the very last second when I played Uncharted 2. It was all I could ever ask for in an Assassin's Creed game, combining a surprisingly fascinating story with excellent, unique gameplay and a world teeming with life and things to do - it was the perfect sequel, not only fixing what AC1 did wrong, but adding lots of things I never knew I wanted.
Well, this game keeps all of that. It isn't nearly as big of a jump forward as AC2 was, however, despite improving a lot of things. The biggest difference in the single player is how much better the 2012 storyline is, but there also seems to be exponentially more things to do in Rome than in any of the AC2 cities (I don't think I could name all of them off the top of my head), with each activity being more varied than those of AC2. Assassin's Tombs return (this time labeled Romulus Lairs), and each of them is more fun than all of the AC2 ones combined... however, the armor that is unlocked at the end comes close to looking amazing, but ultimately just looks weird (I went back to my original, badass custom design). If I had to complain about anything, it would be that there is less tone variation than AC2, which is sort of expected with Rome being the only city.
And then, of course, is the multiplayer. I'm not a multiplayer person (as you may have noticed, I barely ever review multiplayer sections of games), but this was the most fun I've had in standard quick-match competitions in ages. In direct opposition to basically every MP game out there, this game is based on finesse, subtlety and cunning rather than repetition, reflexes and luck. Players that only just started playing can demolish experienced players simply because they played smarter - it's stressful, exhilarating, and frankly the only competitive multiplayer I've properly enjoyed since Battlefield 2.
In a sentence:
Don't let this game's weird half-sequel status keep you from playing it - this is easily on par with Assassin's Creed 2, improving many things at the sake of a few others, in addition to featuring the best competitive multiplayer in years.