If it's SoC, I recommend the Zone Reclamation Project mod for bug fixes and other small tweaks that don't affect the original game play. Complete 2009 makes the game a bit easier but it fixes some bugs as well and has an amazing graphics overhaul.
I'm interested to see what the modding community could do provided GSC builds a new engine. I'm doing an AMK run of SoC right now but I'm really interested in trying out the "I Work Alone" mod for Call of Pripyat since it's supposed to be fantastic. Cheers for Stalker 2 staying in development.
I don't think sales were I problem considering they sold about 2 million copies in 2008. I have to admit, since I saw this, I died a little bit on the inside. I'm replaying SoC for the third time with AMK 1.4 and absolute structures/nature mod. It's so fucking good.