I think it's a great game that builds upon the first one. I finished the game on the easiest difficulty(cos it was the first time I played an FPS on a controller) in about 9 hours, and am playing it again in harder difficulty. Some improvements in the game include the enemy AI, which really adds to the experience. Also introduced are tactical options that let you approach enemies in different ways rather than a straight up all-guns-blazing with a bit of stealth thrown in. I haven't yet played it on multiplayer due to my slow internet, but I'm sure it's great too.
If I were you, I'd get it without the slightest of hesitation, regardless of whether you played the first one or not.
PS: The graphics
