When id Software released Doom they probably didn’t expect it to take off like it did. Previously they did a lot of other games that weren’t nearly as big and the moderately successful Wolfenstein 3D. The point is, everything prior to Doom was nowhere near as popular. Doom expanded upon the graphics conveyed in Wolfenstein 3D and added more detail, more weapons and of course enemies that came straight out of Hell (literally). Transgressing the name itself, Doom also became the moniker of the genre itself when fans would discuss First Person Shooters in general- Doom clones.
There was an actual story to Doom but for most gamers, that was a moot point, they just wanted to click the next button till they were blasting demons. For everyone else, here is the gist of the story:
You are an unnamed space Marine (no, not the Warhammer 40,000 kind) who has a deep running bad streak- you punched a superior officer, though he did deserve it. Punishment for this offense is being transferred to Mars to assist in daily operations of the Marine base there. The Union Aerospace Corporation (the guys that royally screw things up) are working on some wild experiments that go wrong (remember they screwed up). Basically, one of the moon of Mars – Deimos – disappears and you pull the (un)lucky straw to join the expedition to answer the distress call of Phobos. The UAC were doing secret tests in teleportation and somehow it all went down the crapper (imagine that). Shortly after landing on Phobos, as the saying goes, all hell breaks loose.
Doom has seen many sequels and ports to several different platforms. The Super Nintendo even got a port, so did the 3DO (source code release covered here), Playstation, Sega Saturn and more.