Gamepyre published a review of Assassin's Creed for Xbox 360. See also this Assassin's Creed Walkthrough Guide in case you are stuck with this game.

Quote from the review: "If you have a 360, or even a PS3 or just a PC, do yourself a favor and check out Assassin's Creed. The newly released PC version is supposed to have more side missions added in to keep you busy. Whatever system you get it for though, have some spare controller batteries around if you aren't running wired, you'll need them.
This game can draw you in that much. Games like this should make you all happy you choose gaming as a pastime, and manages to deliver on every level, although a tiny bit more variation in missions would have been nice."
Read the full review on GamePyre.