I'm kind of late to the party on this one, but I might as well tell you all what's wrong with"Duke Nukem Forever".
Lack of relevance. Duke was a smash hit back in the 90's along with Spawn and Youngblood. In some ways he was a carry-over from what comic fans call "The Dark Age" of comics where all superheroes were supposed to be 'dark' and 'cool'. This resulted in Superman dying in "the Death of Superman", Batman breaking his back (in "Knightfall"), Green Lantern/Hal Jordan going bananas and trying to KILL EVERYONE (In "DC F'ed up", they kissed the booboo and made it better later) and Spider-man's "Clone Saga" (try keeping up with it, I dare you). To properly explain what actually happened, let me go off on a tangent with some history:
It's normally said that "The Dark Age" was born with the coming of Alan Moore's "Watchmen" and Frank Miller's "The Dark Knight Returns". While both of them had their own political statement, comic editors thought that people were buying them because of the shock value, sex and bloody violence rather than the actual (well-written) stories. So while DC was killing off Superman and Marvel were trying to switch out Peter Parker with some other guy in a hoodie (Ben Reilly/Scarlet Spider, long confusing story). The newly formed Image comics leaped into action with the really good, but also extremely dark and gorey "Spawn" and shot into the air like a magic beanstalk.
Meanwhile in Videogameland, the console wars were well underway. Super Mario's lighthearted Mickey Mouse-like antics were challenged by a blue hedgehog called Sonic from the smaller company Sega. This guy had attitude and was supposed to be the 'cool' alternative to Nintendo's Mario. Sega even went ahead with a pretty agressive strategy:
Now, my basic theory is this. Duke started out as a pretty basic PC-platformer with a guy shooting up stuff. There were tons of those back then, most of them taking place in grey places or sewers. I like to call this "The Grey Era" jokingly. I didn't have much of a console back then (and were barely alive, I'm from 1990), but somehow the developers chose to jump from a platformer and into a shooter - making "Duke Nukem 3D" one of the definitive first person shooters, and even GAMES of the era. People often mention him along with "Doom" and "Wolfenstein 3D" which both changed the world of games completely in their own right. That's a pretty big deal for a game. I have the feeling that Duke was a result of the thought that 'dark sells'. Duke was running around gunning down aliens with tons of gore, and even had the ability to watch half a second of porn in the very first stage on a theatre screen. You were able to give money to a stripper later on. Duke himself, of course, was a huge muscular guy with huge guns and an action movie personality. Every sentence he spoke was literally a quote.
So when "Duke Nukem Forever" FINALLY came out, it was as I had expected. A reminiscence of that weird spot between the Cold War and 9/11 where the only real action most guys got was from pop culture. And that's what I got. A dumb linear shooter.
So why does everyone hate him now? Well, 14 years in development and you come back with linearity and no cover controls in the era of "Call of Grand Theft Battle Shock: Combat Effect"? That's like swinging your junk around inside a nunnery. Things aren't gonna get pretty, and they certainly didn't. People were outraged. "FORCED STORY PROGRESSION?! IN THE ERA OF FALLOUT 3?! OUTRAGEOUS I SAY!" Personally, as a movie nerd, I love the game. But that's the thing. I don't think this is a game for gamers, It's more of a game for... cinephiles? Let's call it a shooter for that one guy that isn't terribly impressed having to live through World War II and Vietnam over and over again.