So much better than the first...
I wanted to like the first Assassin's Creed, but found the mission structure too inflexible. It was a nice looking game, and I enjoyed the running around on rooftops, but the actual game content wasn't what I'd hoped.
Assassin's Creed 2 fixes those problems. While the mission structures are often similar (you eavesdrop, track, and murder, followed by an escape), individual mission feel so much more open and free that it's almost an entirely different sort of game. While the first game's missions felt formal, structured and linear, AC2's feel more organic. There's no busywork here. Missions are straightforward, complicated only in ways that are reasonable (no flag collecting, for instance).
Aside from the main missions, the assortment of side-missions is eclectic and interesting. Even the assassination contracts manage to set up some interesting obstacles. There are a few cookie-cutter missions, but even those will often throw you a curve.
I have mixed feelings about the tomb side-missions. While they are (admirably) very reminiscent of Prince of Persia in their platforming, on occasion the system takes over the camera control, usually during time-sensitive sequences. That might sound like a help until you realize that the controls have subtly shifted, meaning all that work you put into getting Ezio to move smoothly and predictably has gone out the window.
And that takes us to the controls. Most of the time, Ezio's movements are smooth and the animations wonderful. However, it is far too easy to misjudge edges and find yourself jumping into the gap between buildings rather than, say, nimbly climbing across the ropes connecting the buildings. This can be avoided by slowing down on approach, but somehow that just seems wrong in the context of a fast and furious chase through the streets. It's infrequent enough not to be a huge negative, but the game could certainly use some more refinement there.
The game is gorgeous, save for a few minor flaws. The female facial models in particularly are ... disturbing. Mouths too big, often grotesque facial animations. You have to wonder what they were thinking. But the movement animations, from walking to running and jumping, are all fantastic.
As for the story: I found myself more interested in Ezio than the overarching conspiracy/end-of-the-world story they handed us. Ezio's story is wonderfully fleshed out in the first hour of gameplay and then left to flounder. Revenge. Okay, I get it. But I wanted more about Ezio, and we just don't get it. Instead, we get a lot of tired conspiracy-theory claptrap that has been done to death over the last ten or fifteen years. It's all rather silly. The writers took a kitchen sink approach and threw in just about every kooky conspiracy theory out there. It comes off as being ambitious, sure, but in a high-school creative writing class kind of way. Sorry to say it, but it's my honest impression. Less, in this case, would have been more.
Tired story aside, the gameplay here is solid and fun. In short, it's an excellent game, a huge improvement over the last, and I can say that I'm eagerly awaiting the next installment.