Bioshock 1 by far.

Gameplay wise no - but as an SP campaign it was both weaker and essentially hobbled by being uneeded or really adding anything to the existing narrative of Bioshock itself.  The problem Buishock 2 faced was that the original left nowhere really interesting to go in Rapture - the main story was fully played out.  Bioshock 2 - like most sequels - simply fell into the trap of trying to shoehorn something plotwise around the edges of it's predecessor.

The result, as with a lot of game sequels (not all of course) was something that felt solid gameplay wise but less engaging and involving narratively.  I mean look at the obvious "hey, what about a Big Sister instead of a Big Daddy?" mechanic - then they didn't really do anything with it : certainly they failed to match the cinematics and marketing concepts they pushed prior to release about how amazing combat would be with the Big Sister.  To be fair I could say the same thing about Skyrim and Dragons mind - whenever a game promises amazing, astonishingly dynamic combat it always turns out to mean an initially overpowered foe whose moves you learn pretty quickly who will soon, as you power up over the course of the game, come to feel like nothing to be worried about.

Ironically they did come up with a pretty interesting concept (what if you were a Bid Daddy) but then failed to translate that faithfully gameplay wise in that you were clearly not truly as powerful a wreaking engine as the franchise had already established a Big Daddy to be.

Bioshock...but I also like the Killzone and Resistance stories. I havent played Halo. 

Half-Life dammit.

Half life of course

SINGULARITY

None of the above Deus Ex is the best FPS game I have ever played. Though in reality its an RPG/FPS. I loved it of the games listed Battlefields has the best campaign. Halo is the best story however its a tough call. I'd say that CoD has one of the worst.

Bioshock and Metroid Prime are my favourites by a long shot.

I must say I'm surprised by this answer. First because I haven't heard of Singularity and second because you've had a BioShock avatar for as long as I can remember!

While anyone would recommend playing the original over the sequal, as a game Bioshock 2 is still ahead of most other games.

It's inferior only because it's a sequal