I wonder if art directors purposefully choose darkness, or maybe they simply stumbled upon it by experimenting? "We this game to look realistic, and out of all of our mock-ups, darkness wins."

Many Sega games have a very specific look to them that's colorful. Jet Set Radio Future (Xbox) was an extremely vibrant game. Most Nintendo games are too. Though some of those types of games tend to be more cartoonist-looking than realistic-looking.

How about special effects in movies? They use similar technology that's used in video games. Is there a trend here that's more into dark/brown/gray?