Does what a sequel ought to, takes the foundation of the original game and improves upon it in practically every way.
* Very good looking game.
* More interesting side quests and other assorted diversions than the first game.
* Solid game play.
* Good at handing out achivement points, if that's your kind of thing.
Cons
* Side quests are arguably more fun than the main storyline.
* Game sometimes misinterprets which direction you intended on jumping. That's bad.
* Iffy looking facial animation.
Assassins Creed 2 is a very good sequel.
It takes the foundations of the first game and builds upon them nicely.
You play as Desmond Miles who in the last game found out he was an an Assassin and then used a trippy machine called an Animus to relive the life of one of his Ancestors.
The game does an okay job of explaining some of this beforehand.
Well now he's being strapped into the trippy machine to relive the memories of one of his other Ancestors, Ezio Auditore - whose father and brothers were killed and naturally he wants revenge and along the way learns the skills he needs to be a master assassin.
Assassins Creed 2 makes killing dudes fun and provides a good variety of weapons and other bits and bobs from dual wielded wrist blades to maces. Ezio proves to be quite a versatile fighter.
He can use the dual blades to sneak up and take out a pair of enemies at once, unarmed he can disarm his foes and use his weapons to their advantage, eventually you'll acquire a pistol.
As with the original, most of the non-stealth based violence revolves around the use of counter attacks or in the event that a foe is a bit tougher then your average grunt, weakening him so you can get the counter attack. You'd think this would get repetitive but taking on a bunch of bad guys, countering them and picking them off looks and feels immensely satisfying.
The game in general looks pretty good, really.
The environments as with the first game are it's strongest suit.
There are three main cities in the game and a couple of other areas and they all look gorgeous and you'll get to know them quite intimately as you climb and leap all over the environments.
The free running stuff is a tad more satisfying this time, mostly because Ezio proves to be quicker then Altair was. A few games since Assassins Creed have done the free running thing and it's always been a fun way to get around the environments, but I don't think it's ever looked as right as it does in the Assassins Creed series, though occasionally the game will misinterpret which direction you intended on leaping - possibly causing you to plummet to your death.
Like the first game, when you free run you tend to gravitate toward climbable, walkable, scalable, swingable surfaces so mistakes are few and far between but it sucks to be doing well and have that occasion come up where the game does you wrong and you wind up dead.
The character models aren't too bad, though facial animation is a tad awful. Especially on Lucy.
Side quests this time around are more interesting. Perhaps more so then the actual missions.
In the Assassination Contracts specifically it imposes more interesting restrictions and requirements for getting your kill than any quest in the main story line does.
In addition to Assassinating guys you also get courier missions, races and beating up adulterous husbands. Races aside these are a good deal of fun.
I don't have a tonne else to say about the game.
I enjoyed it. I think it corrects some of the things that were wrong with the first game and improves upon the things that weren't, making for a great and satisfying experience.