As I recall, every aspect of the character was stolen from some other pop culture source, making Duke this Frankenstein monster of stolen quotes. If you want to play a funny FPS, go dig up a copy of No One Lives Forever.
Congratulations, you figured out The Joke. The whole point of Duke is that he's a parody of all the other stereotypical action heroes.
I just never found him funny, especially when he quoted Ash from Army of Darkness (Bruce Campbell for the epic win!). That said, I didn't play Duke Nukem 3d in it's entirety, just the demo WAY after it was actually on the radar. I played the original sidescrollers though, and they were quite a bit better then a lot of the other similar titles out at the time.
Other then a Heretic deathmatch with my extended family during their holiday visits, I didn't play an FPS at all until Dark Forces 2, and even then only after it had been out for a couple of years and because somebody else I knew brought it over once. Deus Ex was the second FPS I ever played, and the first one I actually played AS an FPS, since the lightsaber made 3rd person a must.
But back to Duke, I skipped the 3d outing for the same reason I didn't play Doom, or Heretic, or Hexen: 360 degrees of freedom and the lack thereof. In other words, Descent, it's sequels, and then space shooters like FS2. Playing a title with a limited movement cone and sprite based enemies just felt like I was slumming.....low tech and cheap compared to the glory that was Descent (which actually was the first game I ever purchased). Duke's cheesy lines and cardboard cutout personality didn't help matters much either.
That recording somebody made of some random jackass using a Duke soundboard to torment some clan using Vent though was priceless, so you can say that about the fellow.