look there is not much difference between the graphics of AC2 n AC Brotherhood.
They seem to be similar.But in fighting there are lot of new features like u can use crossbow n gun in between hand to hand fight.
There is canon n a tank like machine through which u can destroy enemies vehicles.
Now ezio can ride horse within the city.The area of the cities are now much bigger.
Brotherhood system is quite impressive. Parachute is been introduced along with the flying machine.
Now i come to the multiplayer,
Every Assassins in the multiplayer has his own ability n tactics to assassinate.
There are lot of new weapons in the multiplayer.
I am sure u will enjoy by playing it.
According to me it will be more better than your expectations.
Buddy this is my point of view.
N specially u will surely enjoy its fighting style.Its quite impressive.
By playing it u will get to know its new fighting style features,
Best of luck.