Looking for good single player games

Hey I was just looking for some single player games to play. I have already played portal, portal 2 and oblivion so no need to mention those. So just single player games any that you guys would reccomend.

My PC has 512mb Nvidia Graphic card, 4g ram, lots of HDD space and intel I 5 core processor

Thanks for any ideas :)

stalker: call of pripyat

stalker: shadows of chrnoble

warhammer 40k: dawn of war I & 2

Batman Arkham Asylum!