There's not much that can be said about DOOM and its sequels that hasn't already been iterated countless times before. Whether this is your first time or you're a returning veteran, DOOM offers the quintessential FPS experience. More than just a legendary game, DOOM is a cornerstone that endures to this day, thanks in no small part to a devoted modding community. But make no mistake, DOOM's endearing legacy is owed mainly to its ingenious design, with its easy to learn but difficult to master gameplay. While perfectly playable in DOSBox, it's highly recommended that you find a sourceport to suit your needs. For a vanilla experience that is visually comparable to DOSBox, but easier to configure, Chocolate Doom has you covered. For graphical upgrades (and compatibility with countless WADs and mods), GZDoom is great-and even allows for save states for coop. For multiplayer, Zandronum is a must. And last but not least, I recommend the ZDL launcher to play more complicated modifications (like Brutal Doom). Rip and tear my friends!
Even in its day, this game had many shortcomings compared to other better known RPG's; the dialogue was drab and underwritten, the graphics were questionable, the characters looked like the walking dead, and the story was a slow burn... but underneath all of that was an excellent sense of atmosphere, aided by a wonderful soundtrack. That, and the combat system are still the game's biggest strengths. Older gamers and historians who remember the 'good ol' days' will appreciate this title more than anyone else.