It's a game that you will not forget for a long, long time, lots of fun and a very interesting approach to the genre.
The gameplay and world: this is probably the best thing about the game. You make your way through three enormous medieval cities that look, feel, and probably even smell like the real things. What's so great about it is that you can do virtually ANYTHING in these cities. From walking around the market listening to people talk to climbing the buildings like a real pro - you name it. This is something that is a rarity in games, you can do whatever you want whenever you wanna do it. Total freedom I mean. It's up to you if you wanna fight your way out of a tough situation or escape to the rooftops, you decide how to kill your targets, you play your strikes, and so forth. Even if you have an active quest that doesn't mean you can't go to another city, or take on a new side mission where you are at the moment. Or you can simply just climb high buildings to watch everything from above, which is great fun, because the climbing mechanics is very fun to use. All in all, I probably haven't really played a game that offers you this much freedom. Just climb the highest tower in a town and you'll know what I mean. The gameplay and the whole idea, the mechanics of the game make you feel like you're doing things in the fashion a real assassin in the middle ages would do. All the climbing and jumping and acrobatics look and feel so great, you're gonna think that running on walls like in The Matrix is child's play.
Second thing is the story. It's obvious that the story for the game has been really thought through. In one word, it is flawless. I never expected it to be so interesting and indulging when I first launched the game. Each target you assassinate brings you closer to unveiling something that is very unexpected. You do expect that there is going to be a huge twist in the plot, yes. But the way it actually twists is a huge surprise, and that's just awesome beyond awesomeness. The very fact that there are two stories in the game puts in on a level which is higher than anything else. I don't wanna put any spoilers in here so just try the game, I swear it's worth the money and the time.
The third thing which makes AC so good is the combat mechanics. Ten dudes with swords circle you. And yes, you can kill them all, and it looks amazing. Basically what you do is wait for them to strike and then use the counter attack. And this where the fun starts. The counter attacks are actually counter kills. When you perform a counter kill, you knock your opponents sword away and then perform some really cool moves that kill the guy. You can impale him with your sword, chop his head off (almost, becase it doesn't actually fall off, don't know why) or just cut him up with your short blade. All of that looks spectacular, the camera zooms in to show you how your character moves and that's simply beautiful. Your assassin is a master of the sword, I actually finished the game using only counter kills becase the sequence you get to see when performing one is that amazing. It's hard to describe even, watch the video review! And there are also the stealth kills which you perform using your hidden blade. Breathtaking. Seriously.
So you probably ask yourself why this game got onlu 9.5 from me. Well, it has some minor issues that are noticable. Basically it's that some particular characters and places look the same. But I guess it's something you can't avoid when you got a huge town with literally thousands of peple in it. But these minor thing mean nothing, it's definitely one of the most fun and interesting games that ever came out on the 360. Worth every penny and every hour spent playing. A must-have.