Rapture is what set apart BioShock and it’s sequel from a myriad of other first person shooters. The game design flaws, graphics, and actual gameplay didn’t hold a candle to the setting. BioShock: Infinite was what Irrational set out to make after the release of the first game, and with it they have made a city to rival the underwater metropolis.
Columbia is supposed to capture pure American patriotism and xenophobia to a fascist degree. The city itself rises above the world rather than sinking to the bottom of it.
The game itself should be more difficult than the predecessors in a way to hearken back to System Shock 2. Due to fan demand, Irrational is including a “1999” mode to punish players who don’t adapt to the playstyle they chose. It may not be a perfect fix to BioShock’s initial lack of any difficulty (there was close to no drawbacks to respawning repeatedly), but it’s a start.