Okay, I played Duke Nukem 3D back when it was new and let me tell you-- IT WAS AWESOME!
Besides Duke there was Doom and Wolfenstein, and neither of those had a JET PACK. You couldn't even jump or look up and down!
Duke Nukem had pixelated boobies!
It had really detailed levels that were realistic and fun to explore. You could interact with things in the levels. There were subways you could ride, conveyor belts, doors, cabinets, air ducts, toilets, pool tables (with pool balls you could move), and on and on. Compared to the totally static worlds of Doom it was like like a virtual reality. Doom and later Quake would be more popular, but Duke had the most interesting game engine. Once you snagged a copy of BUILD and could make your own levels it was pure creative bliss.
Of course no sequel could ever recreate that magic. I always felt that Duke Nukem Forever was always delayed because 3D Realms wanted the sequel to be as big of a game changer as the move from 2D side scroller to 3D first person was-- an impossible task.