Hmmm, well I think Randy is right on some levels. Of course "Half Life 2" was ancient at the time Duke Nukem came out. DNF was supposed to be a fairly innovative title, and saying that it was pretty much exactly like an dinosaur of a game from years before it's time isn't much of a defense. To be honest Valve is in an odd position the longer it takes for them to release "Episode 3" because while people expect it to be more of the same from HL2, they also expect it to be more polished and have some innovations within it's conventions.
On some levels I think DNF suffered from it's time in development limbo, as a lot of what it did would have been considered far better, and more innovative, if it had been released on something closer to it's initial planned release dates.
That said, I think the character of Duke Nukem is fine for the most part, low brow humor is fine, and I'd ignore the left wingers who scream about misogynism. To be honest it seems Duke has as many women as fans (just as he is now) as guys, and probably even more. Having watched the weeks up until the release of DNF I saw more girls taking an interest in the title than guys, and doing things like pressuring their boyfriends to take pictures of them (or with them) with various DNF promotional cut outs and such. Really, he himself shouldn't be changed at all.
The problem I had with DNF is that the world was a little too Duke-centric, the entire planet basically being a cult of personality to him to this extent didn't work that well. Duke, and his exagerrated personality, works best when the rest of the world is his straight man. It's hard to laugh because something is "just plain wrong" when it's not wrong for a world that has a "Duke Dome" it's just expected at that point. Done correctly Duke should be exactly like he is, and have everything coming up aces, but the rest of the world should see more or less normal, with the humor in part coming from how everything falls into line for Duke, making him seem even more awesome by association.
In short, I think the franchise should continue, and a lot of the criticisms should be ignored, that said DNF was a mess of a game, but as most reasonable people will tell you, it kind of has an excuse to have been such a mess. "Duke Nukem" is a series I'd give one more chance to get it right.
Oh yes, and those people complaining about Duke's "Misogynism" and how women react to him are those who don't really "get" the game and a lot of it's humor. Duke Nukem was supposed to be offensive to a lot of people, and the people saying that are the guys who are supposed to be offended and justify taglines like "irreverant, and offensive" as selling points. The complaints kind of show that this aspect of the game was nailed, it just wasn't a solid enough game to be embraced by those who DID get it, or motivate many of them to come to
it's defense.