id Software would release several other first-person shooters, but it wasn't until the Doom games that they hit their stride. It has become the most well-known PC shooter, featuring numerous ports, fan-made levels, and has become a gaming subculture in itself. Within its first 2 years, over 10 million people downloaded the game.
Its graphic violence (for its time) caused a great deal of controversy. Much of Doom's popularity came from the support of WADs, (custom player-built levels) and online multiplayer at a time when the modem was becoming widespread.
Doom was superior to Wolfenstein in many respects, from lighting, greater level layout varieties, interactivity (platforms, stairs, bridges) and would go on to inspire an era of games so similar to itself that http://hubstudio.brighthub.com/tools/createedit.aspx?articleId=3967they would be dubbed Doom clones. Doom, a single player, paved the way for Quake, but it would not be long before other makes