Much was said when Bioshock Infinite came out that such a well-crafted world (though admittedly, a bit more like a theme park than a believable city) deserved to be the setting for an adventure/exploration game, not merely an FPS.
I was talking with a friend today about how interesting it would've been if Elizabeth's "quantum powers" had been explored as a puzzle solving device rather than a "summon furniture" mechanic. I feel like that could've been a Portal-esque revolution in gameplay.