The core gameplay remains unchanged in ACII - you're still a parkour free-runner navigating an historical environment, assassinating historical figures that get in your way. That's the franchise's formula, and that's what was best about the first game.
Assassin's Creed II takes that core basis however, and floods it with life. The protagonist, Ezio, is now a much more fleshed out character with a plot driving him. The world of Renaissance, Italy is brimming with life and, most importantly, the gameplay now delivers on the variety that the first game craved. Choice is the key word in Assassin's Creed II, and while there is some semblance of the original game's repetitive nature bubbling under the surface, Ubisoft often do more than enough to ensure you never get bored.
Assassin's Creed II is a lengthy game, with the single-player campaign taking well in excess of 12 hours, and sub-campaigns providing more than 20 hours of gameplay in total.
At the very core of Assassin's Creed II's gameplay is the traversal of buildings and environments. This remains the same as the first game, and is the franchise's key element. The parkour gameplay is such an enjoyable mechanic. Scaling buildings and drinking up the view at the top of them fails to become tiresome - even if you played the first game to death. In part, it's fun because of the game's engine, allowing consistently beautiful draw distances throughout. But in Assassin's Creed II, the whole world is emphasised thanks to the beauty of the Renaissance period. It's dark yet romantic, and constantly engaging.
The worst part of the original Assassin's Creed was the lack of variety. Ubisoft have fixed that. Assassin's Creed II is literally brimming with choice. Most notably, the main campaign often sends you on interesting and varied sub-quests. Of course, as in any open-world games, there are missions that are more enjoyable than others, but the most notable improvement in Assassin's Creed II is the variety. It doesn't matter if you're not enjoying the current mission as previous ones, because you know the game is going to change it up. The game is also a perfect sandbox this time around. There are so many ways to get things done. Want to distract guards? Hire some prostitutes, or throw some money to the ground, or poison one of them, or have them chase some thieves. The game's jam-packed with choice, and that allows you freedom to play it in the way you desire.
The musical score driving Assassin's Creed II is nothing short of fantastic. It's creepy and dark, yet subtle enough to draw you further into the world of 15th century Italy. It's a shame the voice acting never quite reaches the dizzying heights of the orchestral score.
Renaissance, Italy is a great setting for Assassin's Creed II. And Ubisoft really deserve credit for bringing it to life. The game is packed with historical reference and quality architectural design. The game plays with the past for its fiction somewhat, but if you're looking for something a little different from your sandbox game (i.e. not present-day USA) then you'll be positively delighted with Assassin's Creed II.
Altair was a very well designed character, but he lacked personality. Assassin's Creed II's protagonist, Ezio Auditore, is brimming with life. Ubisoft choose to track the character over a large period of his life, giving the character personality and direction. You might not like him, or the choices he makes, but you feel more engaged in him. That makes Assassin's Creed II's story infinitely more powerful than the first game.
With all the improvements made to Assassin's Creed II, the combat still feels extremely clunky. It still hinges on counter attack gameplay, but it's hard to correctly execute these moves and the combat devolves into tedious button mashing.
It's nice that you can opt to play Assassin's Creed II in a native Italian language with subtitles, as it often feels like that's the way it should be played. In English, the voice acting ranges from fine to dodgy, with some questionable performances by side characters and weak accents. It doesn't have any emphasis on the story, but it could have been better.
Graphically Assassin's Creed II is stunning. The environments are rich and the engine is capable of ridiculous draw distances. Sadly, the game's character models are extremely weak. The animation is stiff and the lack of detail makes them look like poor wax models.
Assassin's Creed II's voice samples are prone to looping a lot. During missions it feels like supporting NPCs are broken records. It just gets irritating.
Assassin's Creed II takes everything that was great about the first game and fills it with variety. Set in a much more romantic world with developed chracters and plot, Assassin's Creed II is everything its prequel should have been.