BioShock 2 is the follow-up to BioShock, the so-called spiritual successor to System Shock 2.  Developed by a different team than the first BioShock, BioShock 2's story continues where the first game's left off, and features nearly identical gameplay, in the form of first-person shooting combined with an RPG-lite character progression system.  Unlike the first game, it offers up more moral choices and a more nuanced ending based on them, as well as tweaked combat and an overhauled research mechanic.

BioShock takes place after the fall of Andrew Ryan and Jack's departure from Rapture.  Players take the role of Sigma, one of the first Big Daddy prototypes, who has been mysteriously brought back to life.  Guided by visions from a girl named Elanor, the player must find her and rescue her from the clutches of her mother, Sophia Lamb, who has since moved in to fill the power vacuum left after the first game.  The player also has the choice to kill or spare several key plot antagonists, allowing for the ending of the game to vary beyond the simple good/bad seen in the first BioShock.

The gameplay in BioShock 2 is nearly unchanged from the original.  The player now has the option to use a wider variety of weaponry, and Plasmid powers can be dual-wielded with weapons, allowing for their quicker use in combat.  As before, audio diaries are collected to provide insight into the story and characters in the game, and the player will visit several seedier locations of the city, including its red light district.   Hacking and research have also seen changes to make them faster and more enjoyable.  As a Big Daddy, the player has the option to not just save or harvest Little Sisters, but also guide them around Rapture to obtain even more ADAM for purchasing skill upgrades, and there are more opportunities for brutal melee combat as a result of the player's increased size and strength over a regular human.