Bioshock

Bioshock is a series of games published by 2K Games. It combines elements from both FPS games and RPGs, making it very similar to System Shock 2, which is regarded as its predecessor.

The Games
The first game of the series, titled Bioshock, was released in 2007. The game's story begins in 1960, when Jack, a passenger on a plane, finds himself as the only survivor of it crashing. He soon finds his way into Rapture, a futuristic city on the bottom of the ocean that's full of psychotic "Splicers". Early on in his journey through Rapture, he finds ADAM, a substance that allows the use of Plasmids, which are basically superpowers in a bottle. There are also Big Daddies and Little Sisters, which are a main point of the plot. Each Big Daddy protects a Little Sister, and throughout the course of the game you can choose to fight the Big Daddies, which are much tougher than Splicers.

The second game, appropriately named Bioshock 2, was released in 2010. It introduces new plot elements, and several new enemies, such as the mysterious Big Sister, an extremely fast and dangerous foe, and Brute Splicers, who are extremely muscular, tough and powerful.

Other Stuff
There's Something In The Sea is an ARG that provided little pieces of info about Bioshock 2 before it was released. It followed a man whose daughter was abducted as he tries to figure out where she vanished to with the help of a myriad of clues. It ended when Bioshock 2 was released.