Although Assassin's Creed is incredibly engaging, that alone can't make up for the lazy mission design.
The story also has the potential to be much more than it turned out to be. The supposed "twist" of the game is revealed within the first 20 minutes, and in my opinion, is a total let down. Although the futuristic twist isn't exactly my cup of tea, the story surrounding Altair, The Assassins, and your nine targets does a great job of telling a great story. As you progress through the game, you slowly begin to piece together the puzzle that surrounds the men you are assassinating, and in the end, provides a somewhat open and satisfying ending to Altair's story, but once you go back to your future counterpart, Desmond, the story essentially cops out on itself, leaving you with a bitter taste in your mouth.
My main gripe with the game is it's mission structure. Essentially it's broken into two parts, the first being you must travel to your destination, which is one of the three main cities, Jerusalem, Acre and Damascus. Once you arrive in the city you must report to your local Assassin's bureau and begin to investigate information concerning your target, which for the most part, entails an hour of repetitive and boring pickpocket, eavesdropping and interrogation missions. In order to get to the usually stellar climax of disposing of your target, you're subjugated to an hour of what is an equivalent of watching a Lifetime Channel movie. As for the main targets themselves, the ten or so minutes you spend on the actual killing is very engaging and incredibly fun, but hardly makes up for what brought you to that point.
The game play mechanics are fairly simply, but most of your attacks are automated, which sometimes robs the joy of swordplay. Even though the game nearly sells it self on rewarding you for being stealthy and cunning, the final act pretty much requires you to remain in combat constantly.
The graphics are simply stunning and beautiful to look at, even if you don't have an HDTV (like myself ) you can still enjoy the game for it's beauty. The expansive cities look gorgeous both on ground level and high into the towers of the cities, the latter providing you with jaw-dropping panoramas. The raw amount of citizens on the screen at once are also a graphical wonder, although some models are a little shabby up close, but leads you to believe you are in a living, breathing city in the end.
Overall, Assassin's Creed is an experience no gamer should miss, even if you play it for a couple of hours or rent it. The story, for the most part, is above par, the graphics are beautiful, but suffers from some minor game play annoyances and boring investigation missions, and at the end of it all, leaves much to be desired for a sequel.