Belatedly finished the game just now. I think the readers' verdict at Gamespot is about right: 8.8.
It is visually stunning and creates an atmospheric unique world. The gameplay is very smooth and much more forgiving than System Shock 2. Some of the ideas are inspired, especially the Little Sisters and Big Daddies - they were the highlight of the game for me, especially the scenes were you freed the Little Sisters.
But the rest of the game was less involving than System Shock 2 in terms of the story and empathising with fate of the inhabitants of Rapture. The logs made less of an impression on me - one or two excepted - and there seemed to be fewer subplots in terms of what happened to incidental characters.
It was also not that scarey - perhaps partly because the gameplay was more forgiving (I died a lot and came back to finish off weakened foes). Also, the splicers tended to jump out and rush you more - whereas in System Shock 2, you heard the enemies first. It was listening for them, and having to ambush them, that really cranked up the tension. In Bioshock, the action was too loud and fast to freak me out. I guess I am just not that big a fan of shooters.
I confess I started to find the game a bit of drudge around the time of the big plot revelation. Perhaps they should have varied the opponents, weapons and plasmids more throughout the game. It started getting more of the same old, same old and I ended up just playing because I wanted to unravel the plot, not because I enjoyed the gameplay.
I did not think much of the final boss fight (the boss seemed like he had walked on from the wrong game), but I found the good ending video moving.
All in all, I am very happy this game has been a big commercial success. More games should be like this and Ken Levine, in particular, should never be allowed to become unemployed.
EDIT: Very nice analysis of the Bioshock story here (spoilers throughout); I had not realised it was full of so much symbolism:
http://my.opera.com/noisewar/blog/20...hock-explained
Bookmarks