I look at this game like a bad B-movie. You go into it knowing that it's not going to be good, but that's half the fun. It's a competant shooter, and the big bad enemies are pretty fun. Plus, regardless of the guy hating it so much for it being a slap in the face of other Dukes(You're right, it should have had open maps, that surprised me a lot too), the basic mechanics are fun and he has a sense of humor just the same as I remember it. I even like the little shit, like at the beginning of the game how you can erase and draw on the white board and everything. It's hard to find as much fault as people have with this game.
Are the graphics outdated -- yes, they were when it came out, which is why I waited to get it, but it's still worth 2-dare I say it?-5 dollars easy, if not a little more if you just enjoy the humor.
Everyone hates it so much, that who knows, maybe it'll be a worthwhile collectors item sometime. I mean, it's no Superman 64, so it's definitely not the worst game ever.