In conjuction with the release of the new Left 4 Dead 2, Kotaku have noticed this video(http://kotaku.com/5406163/8+bit-left-4-dead-de+make-arrives-in-january
). A fan made video on how a 8-bit version should be like. This is nothing new, we often see videos on demade on how new games would look if they were 8-bit.
But if I were Valve (the ones behind Left 4 Dead), I would try to pick this 8-bit version up and sell it. Cheap that is, but I think people would buy it. And it would be a great way to market and expand the Left 4 Dead IP.