Assassin's Creed 2 = hours of free running joy!
The good:
1. Ezio's storyline is well scripted, being both dark and humorous. The voice is acting is consistently well delivered.
2. The gameplay is intuitve, with the control system fairly easy to pick up and gradually becoming more complex as the story unfolds.
3. The pace of the game is well balanced. Slow paced exploration is mixed well with stealth attacks, timed quests and open battles.
4. The game environment allows you to approach the game in many ways: you can choose to stay on the side of the law or not, contribute to the economy, complete many varied side quests and puzzles.
5. NPC AI is good: by this I mean that it serves certain functions well without trying to be over complex. For example, when you hire groups, you can issue basic commands at a touch. Any more would add depth, but also affect pace. Plus whilst you cannot talk to every random NPC, they do react to your actions in believable ways.
The bad:
1. The secondary storyline is an interesting idea, though tends to interfere with Ezio's storyline, rather than add anything substantial. This may be because it is referred to infrequently, and appears underdevelped when compared to the main story.
2. The environment cannot really be described as 'open world' because the in-game 'game engine' artificially creates the environment in which you play. The result is that environments are cut off at certain points by white 'static' preventing you from travelling further. This does allow the game to guide you in a linear direction. However, some players may appreciate a large, if limited environment to explore but not get overwhelmed by.
3. The economy is a decent idea to add depth to the game, though does not provide a real sense of challenge. The hunting for treasure becomes redundant once you begin renovating Mario's villa. Plus it soon becomes apparent that you have more money than you can actually spend on items, or weapons etc.
4. Enemy AI is on the whole excellent, though in battles with more than one foe, they do tend to take turns to attack you rather than attempt to corner you as a group. Whilst this is unrealistic, I can appreciate that making battles harder to survive could make them less fun.