Oh wow, DOS games...well, my first PC was DX2 66Mhz so I have a lot of good DOS memories, and I use DOSbox now to get my DOS fix.
So the best games:
-Doom/Doom 2 (this game is still one of the best, especially using new source ports (gzdoom, doomsday) and/or mods like brutal doom )
-X-Com: UFO / Terror from the deep (awesome awesome strategy games, lost countless, not hours, but months on these gems, there is excellent source port called OpenXCOM)
-Warcraft 2/ Command & Conquer (I prefer these two and not Dune 2 and Warcraft 1 due to their user unfriendly controls)
-Halloween Harry/Alien Carnage (love this one)
-Jazz Jackrabbit (one of the if not the best DOS platformer with really awesome music)
-OMF 2097 (lost many hours on the career mode, great game, best menu music)
-Blake Stone: Aliens of Gold (Doom clone with very bright and colorful graphics, me likes; has a bstone source port for win and Vita)
-DOTT,Full Throtle, Monkey Island 1,2 and many others Lucas arts adventure games
-Rise of the Dragon (this is one of my fav adventures, very VERY Bladerunneresque, it could get away as the official BR game)
-Flashback (one of the best games ever for me, finished it 50+ times, the best cinematic platformer)
-Another World (great game, but i do prefer Flashback)
-Dangerous Dave 2 (great fun and hard platformer, love the little cutscenes of death etc)
-Pinball Illusions (DICE at it's best!, IMHO the best DOS/AMIGA pinball)
-Commander Keen ep 4 (up there with Jazz, Jazz is just a tiny bit better IMHO)
-Raptor: Call of the Shadows (yes, I like Raptor much more than the excellent Tyrian)
-Stunts (lost many many hours making my own racetracks
, Mario maker before Mario maker)
-Tie Fighter (best space sim, yes better than WC/Privateer)
-Alone in the dark (before RE there was AITD)
-Aladdin (Mega drive Aladdin in DOS with better sounding music
)
-Blackthorne (blizzard's take on FLashback, not good-not bad...
)
-Realms of Chaos (nice mechanics, good game)
-Fade to Black (not near as good as Flashback, but it is a sequel)
-Need For Speed (the first one in the series)
-Wolfenstein (see Blake Stone...but with nazis)