A great storyline, superb graphics, and various attacking styles outweigh some control issues and the ease of the game.
Pros:
1. Great storyline. To be blunt, I felt Desmond was such a b!#ch in the first game. So it was a relief to see that he could actually fight back, run, and do everything an Assassin could do. But that's just a minor part of the bigger story, which I will not spoil. The main character of Ezio is well established, and you follow his entire development into being an Assassin. It is easy to feel connected to him because his background is thoroughly fleshed out. Plus, I liked how Altair from the first game is a part of the storyline. Everything seemed thought out and well written for a video game.
2. Excellent graphics and sounds. The cityscapes are beautiful, even more so than the original (which were pretty awesome). Characters generally move smoothly, although there are moments that can get choppy (I'm thinking when Ezio opens a treasure chest). The sounds add great ambiance to the environments. People in the city say relevant things, and are sometimes humorous (I enjoy hearing the doctors' remedies that they shout about). Weapons sound effects are sort of basic, but still effective.
3. Numerous attacks. Ezio has many more attacks than Altair had in the first game. You eventually learn some of the attacks over the course of the game, but can even pay a trainer to teach special moves. There is a wide range of weapons, and Ezio can even take weapons from enemies, further diversifying fighting.
4. Numerous enemy attack styles. There are now 3 main types of enemy attack styles, and enemies have just as many weapon choices as Ezio. That means instead of feeling like you're facing the same 2 enemies a million times like in the first game (guards & Templars), it feels like there are around 10-12 different attack styles you need to be prepared for. I especially like the addition of "brutes", which are the larger enemies that you face. Brutes are relatively easy to beat once you figure them out (either use throwing knives, or take their weapons), but when they're part of an attacking group they make it difficult to get out without getting hit. Anyways, having these different styles makes the game more fun.
5. Notoriety. You gain notoriety if you're too public with attacks, which makes guards more alert. However, you can decrease notoriety in 3 ways: remove wanted posters, bribe heralds, or kill city officials. This makes it feel like there are consequences to being very public with kills. Also, it adds depth to the game if you actually want to try to decrease notoriety.
6. An economy. Over the course of the game, you find ways to make money by doing jobs and other assignments. Eventually, you even get to invest in your own villa and profit from it. By the end, you're rolling in so much money that you can't spend it all, but it at least makes upgrading armor, weapons, and your town a challenge for much of the game.
7. Lots of secrets. Since they are secrets, I won't tell too much, but you will have many optional things that enhance the game and fill gaps in the story. Looking for glyphs is one of the most challenging series of secrets. Finding the glyphs on walls and floors is challenging in itself, but once you find them you have puzzles to solve. These puzzles get tougher and tougher and tougher. But they are fun if you like puzzles.
Cons:
1. Sometimes annoying controls. The controls are often described as being GREAT by some, however I have always had a love/hate relationship with them. The controls are extremely forgiving at times, which is both good & bad. For example, if walking to a ledge (not running), you will never fall to your death. Instead you'll stumble & either stop or grab the edge with your hands. This is fine when you're trying to do the move on purpose, but it happens so often when I do not mean to. Personally, I wouldn't mind if I fell when walking because that is actually realistic. Also, the free running is a love/hate for me. It's fun, but it always feels really dumbed down. That can be okay, but there are definitely moments where it feels like I'm not doing anything because free running involves holding down buttons and using the navigational pad. I think the dumbed down controls get in the way at moments, though. Sometimes it feels like the character jumps differently than I was pointing or generally not do what I intended when free running. Fortunately, these flaws are balanced out by the great fighting controls.
2. Limited number of cities. Granted, the cities that are included are gorgeous. Florence and Venice each unlock to be quite large too. However, I almost would have preferred 2 additional cities instead of super-huge Venice and huge Florence. Also, in the original, I used to love traveling by horseback between cities. I used to opt to ride between cities rather than skip. Sure, this games makes up for it a little by having some maps with a large amount of surrounding countryside. However, the quick transfer between cities take away some of the realism of feeling like you're traveling. All-in-all, this is a minor gripe.
3. The game is too easy. Just to state this off-the-top, the puzzles are challenging, and so is a little of the strategy of some missions (like where stealth or speed is required). Also, figuring out some of the sanctuaries are difficult. But the fundamental aspect of the game, combat, is extremely easy. It took me until the very end to die by the sword of an enemy. With medicine and blocking, I could get out of even the most daunting battles of a dozen or more enemies…and 1-1 battles take virtually no skill or strategy. The game is fun on it's own, but it got to a point where I would go into battles unarmed just to make it more fun (I particularly enjoy disarming my opponents & killing them with their own weapons). I used bandits once when it was not required in a mission and I stopped immediately. Why hire friends that make it even easier than it already is. Maybe it's because I was good at the original game (which was easier), but increased difficulty would have been good.