Our perception I believe appears to prefer images with more depth. This is applicaple also with paintings. Dark tones when applied correctly give a warmer impression. Some of the most impressive paintings of the renaissance gave lots of attention not just to colors and detail but special attention was given to shades and shadows as well. They pronounce shapes and detail when they come from the correct angle and the light has the right intensity.I do love colorful games, but I wonder if part of what makes those hard to balance is that we all prefer slightly different shades/tones of colors. Where as the more muted games we are less nit-picky because your don't have a shade or blue that your preference might not like. I really hate picking colors when I am working on level art, it drives me mad moving the sliders around searching for that perfect tone that I want. I show my wife later and she goes blah! (Picking out wall colors, we finally learned to just buy paint and deal with it...)
Or could it also be that the lighting seems better in Gears/The Order with those tones. Fallout 3 for me was not great, and I felt it just look drab. I was playing it a few nights ago and had to adjust to it. Maybe we should take a Fallout 3 image and apply some noise to it?
More colors the more our brain realizes and catches that it is all fake?
Usually very bright paintings look "flatter". For me shadows and shades in a painting are like the bass in music. They give depth. Something similar applies also to graphics. Even if you use the same lighting and the same materials, a simple change of the light placement as well as its intensity does a HUGE difference. The feeling you get is completely different.
Managing the right composition of colors and lighting is just as important as the detail of the assets themselves. I think The Order does this extremely well