BioShock 2 has the unfortunate stigma of being a sequel, and those sometimes seem to not perform as well as their predecessors. Maybe that gives people a bit of a bias against them. Sandwiched in between the pioneering BioShock and the equally novel BioShock Infinite, this game didn’t manage to stand out as much as its siblings. It could be that the setting is the same as the first game, more or less. The game proved to be more refined. It also, importantly, seemed to have characters that felt more alive than the first title.
I highly recommend you return to it with a fresh perspective and give it another chance. It managed to be my favorite game in the HD collection, which was a surprise because I had written it off.