Also: you cannot pretend to be "physically realistic" on a computer screen. The simplest thing: if there is more ambient light, your pupils decrease and your sight is different. You cannot simulate "true light" unless you also simulate that.
Splinter Cell was good here because you could make enemies visible and you not visible by virtue of the fact your character was wearing night vision goggles.
Yeah some games are practically unplayable if you don't completely darken your room and even then contrast depends so much on the display tech of your monitor.