Witcher 1 is a bit dated, are you looking for games in terms of the graphics quality? or games in terms of the post apocalyptic effect to them? Either one I can give lists to, would just rather consolidate said lists lol
If you want to see some of the games I play search this tag in google: ಠ_ಠĦʊღαᾔ ÅυḠмƸИ†ಠ_à²
This is my steam account and if you go through my "all games" youll find some great titles in both graphics quality as well as post apocalyptic affect.
For shooters with fantastic stories I would also recommend [not on my steam list but purchased from a brick and mortar store]:
-Bioshock 1
-Bioshock 2
-Mass Effect 1
-Mass Effect 2
-Deus Ex Human Rev. [in steam but felt the need to add it as I am engrossed in it currently]
Hope this helps, and feel free to specify so I can give you some brilliant game names!