You play as Ezio, who unknowingly joined the Assassins against the Templars because his father and brothers were killed by them. Unlike Altair, Ezio is his own boss most of the time and spends most of his free time killing the people responsible for his father's and brothers' death.
There are quite a multitude of new gameplay elements in AC2, and a few restructuring done. For one, scaling viewpoints and doing random shit before killing your target is removed. There is a distinct line between side quests and main quests. You can actually go through the whole game without synchronizing at viewpoints, pickpocketing or beating people up (unless the main quest tells you to).
Blending in with hired help
A new element to the game is the villa and currency, which adds a certain depth to the game. You can buy weapons, armor, medicine, poison, paintings (lol) and bribe criers. You can also spend your money to upgrade the condition of your villa (your uncle's actually) which will increase the generation of income per 20 mins of gameplay. Honestly, only medicine and armor is useful should you happen to miss a step. Weapons, not so much as long as you have the skills to make up for it.
There are a lot of different enemies too. Other than just archers and plain armored soliders, you now have agile soldiers who runs faster than you and can climb walls like you do, brutes who deal good damage with their axes and durable due to their heavy armor, and seekers who carry spears that can remove you from your hiding spots. I also find seekers incredibly annoying to fight. They parry your attacks and counter attacks extremely frequently. Disarm works wonders against them though.
Hey, it's Vienna afterall
There are plenty of add ons that aren't really worth a paragraph. Notoriety value is a gauge of how notorious you are in a town. The more you make non-stealth kills, the more notorious you get. When it reaches 100%, you are officially a wanted man and that's quite troublesome because you cannot walk along the streets in peace. However, the options for removing notoriety is too good. Tearing wanted posters remove 25%, bribing criers remove 50% and killing corrupted officials remove 75%. You should be able to prevent your notoriety value from reaching 100% easily.
There are some technical improvements here and there. I find that the cities are more alive and crowded. The inclusion of a ton of treasure chests littered around the cities lets you do something on the way from point A to B. Epic climbing stages that exists in hidden assassin's tombs are very fun as well. There are other gameplay improvements like enabling you to kill two guys at once, using pistols, able to swim and poison.
Yes pistols. Made by Da Vinci himself too.
The best improvement I find about AC2 is the climbing speed. Ezio scales the walls of buildings at least 2x faster than Altair, which saved me a lot of frustration should I happen to fall. Also, there actually is a good story to boot, and every mission was packaged differently enough to prevent monotony. With lots of things to find, lots of things to unlock, I almost got tricked into spending too much time in this game.
I think I could just give it a solid 8/10.