Stalker was one of the "best" "real-life" shooters out there. What do I mean by "real-life"? The maps were based very closely on real world places, and the graphics and lighting are very true to life. If you have ever been to Eastern Bloc or Russia you will recognise the "colour and light" of the landscapes. It reminds me very much of my time in Eastern Europe in the 90s. It also has a relevant story backdrop. Loved it. Hammered my system though!
When I upgrade my GPU I think I will give the Complete and Oblivion Lost mods a go.