Depth-of-field is another issue. Our eyes can focus on a fairly narrow focal plane, everything else looks blurry. A computer screen or TV will have absolutely everything in focus, even though parts of the scene are supposed to be far away, and other parts far closer. That’s not too bad, but it kind of makes everything… flat, despite the most eye-popping graphics in any other case. Some games are including a depth-of-field effect, but IMO it doesn’t work very well. The game designers have to decide on an arbitrary focal plane that will be in focus, which means that if you look at anything else it’s blurry. Try to peer off into the distance? Too bad, it’s too far away. Trying to look at something right next to you? Also out of focus.
In film, the director decides what you’re looking at, and there’s a standard sort of cinematography that makes this easier for the viewer.
Yet another issue is that even the best displays don’t have a very big contrast ratio, or very many degrees of brightness in between the darkest and lightest colors. The brightest white is typically a few hundred times brighter than the darkest dark, and even the best current display technologies bring that to maybe a few thousand times brighter. And in between the brightest and darkest of each color, there’s only 256 steps.
In contrast, the real world provides us light intensities covering many more orders of magnitude. Starlight is 10^-4 lux (at the bottom of how dark humans can see), a full moon is .27 lux, well-lit interior is a few hundred lux, and direct sunlight is over 100,000 lux. Although we can’t perceive all of that at once, and our eyes adjust to the conditions. Still we can perceive a lot more contrast than displays will give us, and with much finer gradation (though 256 steps seems pretty smooth over the range that monitors can display).
In a game, the darkest room looks like a matte black piece of electronics in your living room (oh hey, I need to dust…), really just a darkish grey. And the brightest oversaturated in-game sunlight is an even white, probably less bright than the light fixtures nearby. A proper movie theater can improve on this, but only by so much.
In terms of color depth, that means that the best displays can’t provide as much visual information as we’re capable of seeing.
Some games simulate the human response to changes in brightness by HDR. Here, the graphics gives as much contrast possible to the scene, saturating bright objects in a mostly dark scene, for example. When the game moves from the dark to the light, it simulates adjusting eyes as well. It looks pretty good, but it’s still an attempt to fool us into perceiving more than is really there.