In Russia, S.T.A.L.K.E.R. is very popular, and many almost consider it a Russian game. Personally, I haven’t played Russian/Ukrainian games, so I completely missed S.T.A.L.K.E.R.
stalker is a fun game... it's like Elder Scrolls: Nuclear Psi Doomsday... lots of progression to more cool weapons, equipment, more interesting anomalies, better artifacts, and then in Call of Pripyat they added a whole weapon/armor upgrade tree as well... the original is a reallllly long game, i mean, takes weeks to play through it