First off, I loved the first BioShock, it was a great game experience, very cinematic, fun gameplay, and a awesome story.  
And I always like it as a stand alone game.
To me there's no reason for a sequel, unless it has a good story.

Which brings me to BioShock2, it seems like a cash in, plus it was made by a different developer.
There's no reason for a sequel, unless it has a good story.
 So is there any reason why I should  bother with this game?

meh.  The game is solid, if not as good as the first one story-wise.  Actual gameplay is better though, but since

A lot of people hated for a number of reasons but for those who played, they said it was a solid game, gameplay wise. The story itself however, feels more like a footnote in the history of Rapture so don't expect much.

I've started playing Bioshock 2 just the other day, because I've finished Singularity and fell in love with those storytelling- atmospheric FPS all over again.  As Jeff pointed out in the review, the star of the series is Rapture. If you like the sole atmosphere of Bioshock and Rapture you should go for it. If the story is such a big hook, then probably not, I would recommend Singularity then if you want a new original tale. 
 
P.S. As far as I can tell by now (I'm a couple of hours in the sequel) the gameplay and controls are much much better then the first one.

I really enjoyed the game. The story was pretty good considering what it had to work with. Gameplay wise, I loved it. Great game. Get it. 
 
GET IT.

Bioshock 2 is a great game that shouldnt have been made, but I think you can get it for a good price now so go for it.

Yeah,I'll probably get it eventually,I need to get some money to spare though.
 
It sounds like a good game,It's just I think it'll be hard for it live up to the first ones original feeling,of the creepiness of rapture.

It's a useless game that isn't as good as the first, but it's not terrible. I would probably rent it thogh.

I kind of turned away from this game after hearing it wasn't worth it "because it just sucks", why did I listen? After reading peoples opinions on here I think it is something I would enjoy. I loved Bioshock. I found Rapture incredible and had a great time exploring it as well as following the storyline. I don't really care if Bioshock needs a sequel or not, fact is it has one and fortunately it looks like something I'd like to play!

BioShock 2 is a great game, it just isn't the 'holy shit!' masterpiece the first one was.
 
Anyone who says its a bad game hasn't played it and thus has no right to voice an opinion of it.  The gameplay is solid (actually better than the original for the most part), the story is good, the new characters are interesting and theirs a nice twist at the end not to mention multiple endings depending on your actions. 
I'm on my second playthough right now, bought it during the recent steam sale and I don't think I would have minded buying it at full price had I known it was as good as it is.
 
So ignore the cynics who love to hate things because hating things is cool, its a great game, not in the same'league as the original but well worth buying and playing.

Wow, this has been really helpful,I thought it looked like a good game but I just didn't want a sequel that wasn't needed.
It seems like it has some cool combat,but I've heard that it was lacking in story,but now I'm hearing it has a good story,or a descent enough one worth a play through.
I just loved the feel of the first rapture,so I didn't want to tarnish my opinion on the first game.

I think so.

Frankly, they didn't do anything wrong with the game, it just wasn't as good as the first. So buying a cheap copy, renting or borrowing off a friend seems like the best thing to do.

Yeah they just made the first one too awesome.

I preferred the second game, the story is a bit slow to start but still great. The opening of the original BioShock is much better but on the whole this game meshes together just as good, the audio logs are top quality and the game feels very solid. More fun to play than the first as well due to the improved combat, the new weapons are quite fun too.

I actually just finished it. It's really a completely different experience. I felt like 2 was a lot more creepy than 1, but 1 was much more awe-inspiring. You get to learn a lot about the backstory of Rapture and the morality is a little more in-depth than simply harvesting or saving the Little Sisters. It's not a bad game, but it's not the same revolution that the first game was. That said, you can probably find it for REAL cheap nowadays and it's definitely worth that price.

It has a good enough story to keep you playing and the gameplay is improved. So yeah, you should buy it.

I felt like it showed how Andrew Ryan lost his grip on Rapture better than the first game which too broadly painted him as a megalomanic. 
 
The gameplay is better and the multiplayer fun.

If you liked Bioshock 1, you will like enjoy Bioshock 2.   It's more of the same, just as fun.