are you playing the game in windowed mode? if so, check your wallpaper, the game tends to look not so dark if it's behind a dark wallpaper. Also, I would try messing with your graphic settings a bit.

What type of monitor do you have? Is it more recent? and does it have a higher brightness/contrast ratio? The game looks just fine on my monitor, even in the dark... but i'm also using digital output via HDMI.