I found Bioshock 1 to be very intriguing.
To bad its so linear, I think a game like that needs to be more open ended, even if its just to see more places and find out more about the freaking near post apocalyptic underwater world your in.
I mean come on such a great collection of unique, cool and bizarre ideas, but its sort of wasted in the fact that you progress down the same old corridors but all that seems to change each time is a new gun upgrade or some new ammo you took from the millionth identical splicer you killed.
Stalker Shadow of Chernobyl i found pretty intriguing as well.
Mainly the plot which makes you wonder just what happened to the amnesiac protagonist for once.
Oh and the fact your in a strange world full of mutants and different factions of heavily accents Russians trying to constantly kill each other.
The plot seems to solve itself too quickly, but your in a world where weird, crazy, scary cool stuff happens.
Unfortunately you dont get much information from NPCs on just what the hell is going on.
But that makes it sort of feel like everyone is accustomed to the everyday life of trying to not get eaten or shot for another day, which kind of makes the world more intriguing.
The problems it had, mainly lack of side missions, the bugs and crashes and the fact you get the best weapons and armour within 2 hours are fixed with the most recent Stalker game, Stalker Call of Pripyat.
I like this game so much that i reckon the only bad thing worth mentioning is that there needs to be more of it.