Duke Nukem (Duke Nukum as defined in the game) is a very old platformer created from the success of Commander Keen. The game more than pleases you with it's charming hue and extensive saturation. The game comes by no means near any standards of gaming today; there's no music, the sound is so minor (sound can actually play from your internal computer's tower if you lack a speaker, yes, the game is so old that that was a thing you could do), the graphics are resemblant to what one would consider "between the NES and SNES generation" and the controls, likely, are styled for older keyboards and times of the past. Now what do I say to cover those issues? Get over it.
Let's not forget this game came out in 1991. For the time, absolutely everything about it was impressive (even today the level design draws attention). Take your mind off the issues of Duke Nukem and enjoy the platforming excellence there is to spot. Hidden areas, lucky loot, surprisingly fun-to-rack-up highscores, somewhat developing storyline (though barely), unique scenarios and difficulty set this game as in my opinion one of the best DOS platformers in existance.
Accept the substitutes or not, Duke Nukem is just slightly less fun than I assume it was in 1991.