Bioshock is stunning, and that more than makes up for the lack of variety.
This is the feeling I got when I caught my first glimpse of Rapture, the huge, majestic underwater city in which Bioshock takes place. There are many moments of awe such of this throughout the game. The impression this gives is that Bioshock is less of a game and more of a work of art.
It would be easy to think "So the WHOLE game takes place in an underwater city? Wouldn't underwater city get a bit boring after a while?" The answer to this is of course no; each new area you enter is drastically different to the last. From the grotesque cosmetic experiments in the medical pavillion to the icy halls of Fontaine fisheries, from the thick vegetation of the garden district Arcadia to the thoroughly disturbing attempts at fine art in Fort Frolic. If there is one problem about the whole game taking place in Rapture it is that it could make you feel claustrophobic. I have never been remotely claustrophobic and yet I had to take regular breaks because I literally felt like the walls of Raputure were closing in around me, which really says something about the successful portrayal of the city.
The gameplay of Bioshock is very good, but nothing revolutionary. It plays like a standard run and gun shooter, but if you've played a few tactical shooters you can carry your tactics over to a certain extent. The main enemies of the game are splicers, which weild pipes, pistols, machineguns, meathooks and plasmid powers. Most of the areas in rapture are pretty non linear, allowing you to catch your pursuers off guard by circling round a different path and shooting them from behind. This is difficult though since the splicers are pretty perceptive.
The plasmids/gene tonic powers essentially offer some character progression and some hilarious ways of killing or stunning foes. There's the electrobolt, which stuns enemies so that you can whack them with your trusty wrench, incinerate, which sets enemies on fire, and many others including cyclones that hurl enemies into the air.
Unfortunately less halfway through the game you'll meet the final type of splicer of the game. From then onwards instead of fighting new, interesting enemy types you are fighting the same ones as before, but with steadily more and more health. I'm sorry, but in ANY game a shotgun blast at close range in the face should be instant death to all but the most heavily armoured foes. Giving enemies more health because it doesn't make the enemies feel stronger, it just makes your weapons feel weaker. In the later stages of the game you will likely get pretty frustrated at how repeated blows to the head with a wrench fail to put down the very same enemies you were happily bludgeoning to death in the earlier levels.
Now I casually make some games myself and I know that a decent rule of thumb is that a very skilled player should be able to avoid taking much damage if they play their cards right in any of the games situations. This unfortunately isn't true of Bioshock. You can be drilling a splicer in the head with a machine gun and he will still manage to fire his pistol back at you and not miss. Even being set on fire doesn't seem to hinder the splicer's ability to fire guns at you with sharpshooter accuracy. Even the stunning attack becomes nearly useless in the end due to the fact that whacking a stunned enemy with your wrench seems to instantly cure them of their electricution. This is a common shooter pitfall the which the game becomes less about outwitting your enemies and more about who can shoot faster and how many healthpacks you've collected.
One of the reasons why the splicer health increase is a bad idea is because it is irrelivant anyway. Why? Because every time you die you get resurrected at a ressurrection station, with everything exactly as it was when you died. "I for one plan to keep you alive" says Atlas, well thats really big of you since its impossible for me to die. So effectively every enemy in the game is not a threat, but simply one who will delay your progress. This sucks out a lot of the tension of the game. You don't fear for your life because at no point in the game (save for the very end) is at actually at stake. Want to take out a big daddy but not tough enough? Sure thing, just keep respawning. Trying to make some headyway into a splicer infested area? Keep respawning. Splicer gets the jump on you? No problem, because the spawn o matic is here. Oh and good thing the splicers can't use it aswell or you'd have a lot of trouble shaking the angry horde of splicers who you've previously killed. I really hate it when games try to find ways around dying. Its stupid. Part of the challenge is the risk of failure and if you can't die then there is no risk.
The Big Daddies are one of the awesome things about the game. They won't attack you unless provoked, but you pretty much have to fight them if you don't want to spend 100 hours completing the game because taking down the daddies is how you get your plasmid powers. The fights are intense and difficult and you suffer heavily for not planning out your attack beforehand. Again though the fights would be made orders of magnitude more intense if you couldn't indefinitely respawn.
All in all the gameplay of Bioshock is very good but suffers from some bad decisions from the developers in my opinion. The gameplay isn't that important in the long run though. It's the feeling of awe that the fantastic art direction, incredibly well voiced characters and deeply unsettling sound and music that makes Bioshock an amazing experience.