Unfortunately, it's simply not feasible to play every game at the default or lower gamma settings - gamma correction was introduced in order to make it possible to play the game in conditions where it would be otherwise impossible to see darker spaces. However, if you are correcting external light, the results look rather garish indeed. The image looks quite washed out, even though it really is not, because it brings up lower colour channels that may not have been intended to be brought up so high.
Spoiler: Uncorrected Scene
Spoiler: Gamma Correction 2.0So - what this mod attempts to do is restore some of the colour vibrancy so that gamma correction looks better. While it doesn't magically make Doom playable with a sun glare on your monitor, it still looks a hell of a lot better when you try to correct it:
[spoiler="Clean" Gamma Correction 2.0][/spoiler]
This version is controlled by "gamma2" - nothing more. Simply set gamma2 to your desired gamma value.
Spoiler: Old version