personally it's my favorite Assassin's creed game, the first one dragged the fuck on with it's long unskippable cutscenes where nothing happens save for two guys talking in a library...one of which is always spazzing out and walking into walls as some form of amusimg myself
the second one probably had the best story out of all of them, a likable protagonist, interesting narrative and the historical setting was much more vibrant and well realized than in any of the other games, thing is i really don't like how they stretched Ezio's story out over 3 games, he was great in the the first one, but by Revelations i was just tired of the guy. it's also incredibly easy...too easy, and it only got easier as such the combat in revelations was just laughable
the third one takes the cake for me as they finally figured out the combat, sure, you use the right weapon and it's a cakewalk but i choose unarmed combat throughout most of the game, only ever killing my targets and no one else, it made me feel a hundred times more badass than if i had just killed them all. plus in my opinion the parkour and freerunning flows better in AC3 than in any of the other games, it just feels more fun than in the first 4 games, and the fact that the buildings were shorter only added to that, i never had to slow gameplay down just to climb a particularly tall building, most all of them were a pretty comfortable height, plus Naval combat was entirely badass.
and in terms of story AC3 wasn't bad in my opinion, the protagonist could've been more interesting yeah, for both Desmond and Connor, but the story unfolding around them was certainly enough to maintain my interest...the Revolutionary story at least, Desmond's story absolutly sucked, they didn't show nearly enough of it, none of the modern day missions were as cool as anything going on in revolution era America, they killed off both of their interesting villains long before the climax and of course the ending was horrible...not as bad as the original ending to Mass Effect 3 though, at least in my opinion, because A. it isn't the absolute end, like ME3's was, this same storyline will continue on to future Assassin's creed games, so there's that and [spoilers] B. it got rid of Desmond, leaving behind Rebecca, Shawn and Desmond's dad who are infintely more interesting than Desmond himself [/spoilers]
so yeah, not prefect, but i freaking loved it, no where near the worst AC game, not while Revelations and now Liberation still exist