"The ending of the first Bioshock didn’t seem like it left much room for a sequel that could hold its own weight but it seems like Rapture has a few more stories about its lore and inhabitants that need to be told. Bioshock was unlike anything we’ve seen before which is partly why it did so well, so having a sequel made me wonder what could be done new to avoid becoming stale.
We know from what happened in the original Bioshock that Andrew Ryan was the mastermind behind the underwater city of Rapture and how the uncovering of ADAM eventually led to its demise and the overrun of Splicers."