The first thing I really paid attention to was the graphics. Despite a 3 year gap between games, There was no difference in the quality of the visuals in comparison of the two games. If anything, This game looks worst. And that's mainly because it's utterly broken in the last 1/3 of the game. There are just so many annoying bugs and glitches (floors are black, you can see through walls, characters have no heads) that it makes an already so-so game even worst. And on top of that, The environments are very heavily recycled and it's very tiresome to look at after a few minutes let alone hours.
Now the gameplay is pretty much the same as it was in the original game. I think the melee aspect of the combat is a bit disappointing, It doesn't feel right and can be quite frustrating because it's so easy to miss. What really irks me is that playing as a Big Daddy is no different than playing as the human character in the original Bioshock. They couldn't add one original thing to make it a unique playing experience. Instead, it's like playing in a different skin so what's the point in having a story based on you playing as a Big Daddy when there's nothing different about playing as one?
As for the story, It was mediocre at best. It didn't interesting me in the slightest. The campaign wasn't that long either and only took me 10 hours to beat. It was a very straightforward point a to point b style campaign, No room for exploration like the first game, Which gave you multiple levels and areas to explore. The campaign was a huge letdown. I loved the story of the original Bioshock, I loved exploring Rapture. In this game, There is none of that. It just is. And I feel the main reason the campaign suffered is the addition of the multiplayer.
The multiplayer itself is absolutely pointless. There's a reason they took it out of Bioshock Infinite. Nobody wanted it in the first place and Bioshock 2 suffered greatly because now instead of having all your efforts on an amazing campaign like the first game. They're split between making a sadly sub-par campaign that is supported by a rather weak multiplayer.
Bioshock 2 suffers from a campaign that is totally broken in the last 1/4 of the game and a weak multiplayer that no one wanted in the first place. It's a shining example of everything you shouldn't do in a sequel.