I loved the game. People seem to think that the actual DNF that they're playing today was in development for 14 years. Yeah, of course it was, it's running on the Quake 1 engine currently! But seriously, the game we got was in development for 3 or 4 years, 3D Realms just wanted to get it done, because if they tried anything ambitious with such a small team, they would never have finished it. It was possible in 2001, but not anymore.
Problems with the game:
The humor and interactions with npcs was done... wrong. First of all, most of the characters you meet on Duke's adventure should have been serious and scared (like in the 2001 trailer, the best game trailer of all time in many people's opinions), not all cheesy and making jokes left and right. Duke would then say things that were funny, and that would have been a nice balance. Duke's world was not about being completely hilarious and stupid, it should have been somewhat serious and epic with Duke doing/saying funny things.
Also, Duke only spoke in a conversation once. "See you at the party." That's it, and even then, it doesn't add on to the current conversation at all. Duke should have talked to NPCs, and commented on their emotions all the time. When you saved the babe from the falling elevator? She says "lol duke thanks [sexual joke]." Duke should have said something, like, "Whew, that was close!" or, "You okay?" Perhaps, even ask a question to point out the player's next goal. Duke not interacting with the npcs is a giant waste of potential.
The humor at times was just terrible. The hive level was this freaky, very disturbing level, and then you see the twins and they've been impregnated by the aliens. Instead of Duke showing some sort of realistic, but still Duke like... emotion (which can be done well), he says "[lol lame joke]," and then they explode. Then he gets angry. So they're in danger, Duke jokes about it, they die, he gets angry. How about just being angry all the time?
Vegas was at day. Yeah, it's something new... but it looks like shit.
The very cool health system was removed for a very generic one. Before, when you killed stuff, you would regain health. So when you were low, instead of hiding and wiping off blood from your sunglasses, you would try to make a final stand like in a true action movie to get your health back. It was perfect, who thought they needed to change it!?
The 2 weapon system is poop. The reason they implemented it was because they couldn't get weapon selection to work well on a console. It's called a weapon wheel...
Blood decal bug. Basically, blood decals don't appear in the game, so the gore is reduced by quite a bit. I mean, I don't need gore, but it's Duke Nukem!
Long load times wasn't a problem for me as I played it on the PC, but the fact that Gearbox ported it so poorly sucks.
[Insert many more issues with the game here]
Anyway, the game was a lot of fun for me. In fact, I didn't have that much fun with an FPS in a looong time, so it really was a good game. I feel disappointed the more I think about it, however, but whenever I play it again, the feeling disappears. If I had to give it a meaningless number, I'd say 7/10.