Another amazing story from the sea !!!!
Half of the narrative force in the first game derived from the setting itself; as you progressed through Rapture, you learned more and more about its history, unraveling a tale of a noble experiment gone horribly wrong. Rapture was its own ecosystem, and it took time to learn how to live in it and adapt to its utterly insane but internally consistent set of rules. The satisfaction from its combat sequences wasn't necessarily from the breathtaking pace of the gunplay or the high intensity of scripted sequences (as in other shooter series such as Call of Duty, for instance). The joy derived from using the environment to your advantage -- hacking security cameras and turrets, laying traps at crucial points, and turning enemies against each other.
Bioshock 2's mechanics are fundamentally similar, but the mystery and discovery are gone. That the game lacks the original's sense of mystery is almost unavoidable and is not a criticism of 2K Marin's work on this project; but it does hamper one's enjoyment.
Ultimately, Bioshock 2 remains a very good game. Combat, if anything, is smoother than before thanks to the ability to wield plasmids and weapons simultaneously, meaning you need to do less pausing. The pace of combat picks up and feels more frenetic than before (in a good way), and you'll especially feel the adrenaline rush during sequences when you have to guard a Little Sister while she gathers Adam for you.
I encourage all gamers to return to Rapture. Just don't come in with sky-high expectations, and you'll find a lot to enjoy in this well-made sequel