CommonNinja on 08 July 2014
Part of the reason is because you played it late. The benchmark for storytelling has raised enormously over this past generation.
Back when Bioshock came out, it inovated on a number of fronts:
-Atmospheric storytelling
-New mechanics (plasmids and such)
-Sound Design
Bioshock has aged well, but as time goes on, it begins to seem less impressive due to the bar for immersive storytelling being raised by games like TLOU, Allen Wake, Mass Effect, or even Journey.
It was amazing at the time it released which is why it stands tall as one of the best games of the generation. If it was released today, it would still be considered a "good" game, just not near as groundbreaking.
