Whilst the FPS genre has since had a tonne of fantastic franchises, such as Quake, Unreal and Serious Sam, Doom remains at the top of the pile, and has one of the best comeback stories in video game history. Doom is almost 30 years running, and has even bled into other mediums such as feature films and novels. As it has been going for so long, there have been a large number of entries in the series, and there are probably a few you never played. This is every Doom game ever.
Source: N4G PC Every Doom Game Ever