I played Bioshock 2, although only for about half an hour before uninstalling. The main reason is the wrong feel. In the end of Bioshock you put on the suit to mimic a big daddy, controls changed you felt like that massive heavy chunk of charging apocalypse. In BS2 that feel disappeared, you were agile and thus it felt like you are literally just a dude with a fishbowl on your head instead of a proper big daddy.
So no, my dislike does not come from the notion that it is a cheap knock off, but because the game mechanics that I experienced for a short while in the end of the first game were screwed up in the second. As for the concept I would rather explore the prequel with the turmoil that happened in the city, further delving into the theme of science vs ethics instead of exploring tools and by-product of that unrestraint science.
Still, the new Bioshock has new setting, so I will welcome it open mindedly as soon as I check that game mechanics are in order.