Yeah mp co-op is pretty cool, but I really just want something that I can spend 30min - 1hour on once a week or so just do hunt the AI terrs when I'm bored.
I think I'll give Vegas 2 a go...
Smith & Wesson Jr was a son of a gun.
ARMA2 was released last year, but you have to be heavy into simulation games, and need 3 keyboards worth of buttons to play. Very realistic though but too much simulation for fans of normal FPS shooters.
My recommendations might be slightly off your wish list, but FEAR2 was really awesome and as a third person tactical/RPG I definitely recommend Mass Effect 2!!
Further, what these guys said, MW2 is worth playing, there is no constant enemy spawns - if you kill them they're dead and you can move on; they also did good work with the AI, they can be quite challenging (on the harder difficulty levels of course) for example they will stay behind cover, shoot from cover with only their arms showing and pretty much pwn you if you're not careful. Try it, you wont regret it.
METRO 2033 was off the hook, little disappointing ending but its the journey that counts
There is a Hell, Believe me, I've seen it. If there was a Heaven, I'd keep it a secret
Co-op can be pretty cool, been jivin' Rainbow 6 vegas with my bro for a while now.
The singularity is about to explode! Weapons are at maximum.