Compared to other entertainment mediums like film and television, gaming is a mere infant. Despite this it has made huge progress in its forty plus years of existence. In the time it takes from a baby to grow into a man-sized baby and then a slightly wrinkly, greying man-baby, gaming has leapt from two dimensions to three, from arcades to living rooms and from living rooms to our pockets. Its got to the point where people can play Doom on an ATM and printers can play Mario music. Quite simply, games are everywhere. Gaming has changed for sure, but there is one rule that has been present ever since the beginning: in every console generation there are a handful of games that shock the industry with ground-breaking, innovative features that are then shamelessly copied by developers hundreds of times over. The following 20 games are so important and innovative that gaming as we know it today would be very different without them. Love them or hate them, they came up an idea that set off a chain reaction that made our beloved industry improve, expand and reach a wider audience. That can only be a good thing, right? Lets begin!