Plus, it came with a level editor! Oh, the hours I wasted with BUILD.EXE...
Dude, none of the things you mentioned in the level design were possible in Doom's engine.
I think you are right. I remember Duke as technically more advance than Doom 2
I found something here: http://doom.wikia.com/wiki/Duke_Nukem_3D
"While Doom and Duke Nukem 3D feature similar technology, Duke Nukem 3D could in most respects be considered technically superior. The player can jump, crouch, and aim up or down. The rendering engine features slopes, overlapping and moving sectors, arbitrary scaling of textures and strong scripting capabilities"
Ah, chalk it up to fuzzy nostalgia. I swore that the mirrors actually were functional, and you could damage stuff that was on the sidewalk with the boot-kick. Maybe I'm mixing it up with other FPS games of the time. It's been a while.
The Duke Nukem engine was (from my point of view) on par with Doom's engine, but their level design made playing the game a lot of fun. From seeing yourself in the mirror, to kicking toilets and fire hydrants, the world seemed much more alive than any other game at the time.
The game had a fun boy-ish "I'm gonna kick ass" vibe to it that isn't really seen today. Most FPS action games nowadays, while fun and entertaining, seem to take themselves too seriously. Musclebound Marcus Fenix is too brooding, and Roach too focused on terrorist plots to really portray the giddiness that was found in kicking a pig in the face with your manly boot.