The MOST realistic shooter ever ran on my PC!
Two most important elements contribute to the high level of realism and immersion; graphics and human simulation.
In terms of graphics, this game plays like a holliwood movie! Everything is photo realistic with proper focus, blur and depth such that it doesn't feel gamey at all... in fact, check out some of the videos or screenshots and you can hardly tell if those are photos or ingame shots!
In terms of human simulation, the headbobbing, the world going blur, the heavy footsteps, the body movements, the blurring on getting shot etc all makes you feel like YOU are the one in there!
Experience it to understand!