STALKER - original game - has one of the most complex AI that exist .And after the first or second patch has little bugs , especially under Windows XP It is difficult to compare with another game. Not only the combat , you can see all the features of AI in a living world and with factions that are discarded in games like Far Cry 2 or are ridiculously simple.
You can see more bugs in the ridiculously simple Assesin, s Creed - tons - that in STALKER. The only difference is that the former is a game for casuals, maistream type game with a big company and a with two boobs behind . STALKER only has the money of Sergei Grigorovich , which is a lot but not as much as Ubisoft.
Yes the AI in Cryostasis is not good. But you have to consider that they are zombies, an can not ask for this type of enemies a sophisticated AI . In any case, it is not good, was flawed. But .. Cryostasis not is a FPS or not is the most important part of the game. I do not know why you think it is a FPS, most of the game you do not shoot a gun fire .
For me it was what had to be, I do not want in any way something like Stalker CS or mods for STALKER that activates all the features of the game that do not work in any way. And
Cryostasis is similar for me , the game does not need to be another FPS like Doom 3 in a corridor to be a great game