According to Valve's blog, this was one of their goals in creating the box art for Left 4 Dead.

...under no circumstances would we use Photoshop. L4D is a visceral experience, and its box art deserved the same approach. Valve artist and L4D1 hand model Andrea Wicklund was more than happy to help.

The box art for Left 4 Dead isn't iconic just because the game is so popular, although that helps. It's iconic because it's simple, informative, and bold. In other words, it's risky. If Sony, Electronic Arts, or Activision was responsible for the cover, it would have a picture of Francis, Bill, Louis, and/or Zoey, bristling guns. In the background would be a busy cityscape with zombies. It would be a noisy jumble designed to stand out, but because it would sit on a shelf next to a bunch of other noisy jumbles, it would blend in.

I wish other game developers would take to heart Valve's approach. So many videogame boxes are driven by marketing research, which dictates a dude (or chick) on the cover ("Gamers identify with a character"). Action stuff happens in the background ("Gamers want to know the gameplay is dynamic and exciting"). There are probably guns or tanks, maybe an aircraft ("Gamers love hardware!"). The game name is some sort of arresting in-your-face font ("Branding, dontcha know?"). Lots of busy activity ("Remember, dynamic and exciting!").

It's all so unimaginative and rote.

It's a shame more game boxes don't do something simple and memorable. From there, it's not a far step to iconic. Red Faction: Guerrilla came close. The box cover features the stencil image of a fist grabbing a hammer. But THQ went and cluttered it up by dropping in a picture of the main dude ("Gamers identify with a character"), a walker ("Gamers love hardware!"), and hints of wreckage ("Gamers want to know the gameplay is dynamic and exciting").