Fallout 3, but it's impossible to commend the game for its lush, rich environments. Pools of standing, radioactive water? Yuck. Shelled-out buildings inhabited by sallow-skinned mutants? No thanks. Go ahead and say it was intentionally designed that way to create an unsettling, hopeless atmosphere -- we know a sorry excuse when we hear one.
Thankfully, a modder by the name of Khyrin recently released "GreenWorld," a Fallout 3 patch that brings some much needed arboreal splendor to Washington D.C.'s unsightly landscape. You can download the mod here, then watch as Fallout 3's grotesque, sepia toned pallette is exchanged for something a little more viridian.