Which version of the game did you play? Or did you even play it at all? The console versions sucked, they were horribly rushed ports of the PC version. The game was designed as a 90's FPS shooter with platforming elements.
Here is a much better honest review of DNF
http://www.youtube.com/watch?v=Th2z0xT-X5s
Score should of been a 6.5/10, mediocre yet a decent game.
-=Edit=-
If you basing any amount of your opinion on either the PS3 or 360 release of the game, then stop right there. Having seen the absolutely HORRIBLE disaster that the console versions are, it's just not indicative of the PC version. The console versions look like they scaled all textures down by a factor of 4 and reduced the model complexity by a factor of 10. Lots of popping and horrible controls (it was designed for keyboard + mouse). I have played through the PC version and it's just fun, not a masterpiece but definitely enjoyable. Not worth the release price of $60 USD, would of been better as a $30~40 USD game. PC version loads faster, has no graphical glitchs, has 2011 era graphics and zero control issues with a WASD + mouse setup. About the only thing I can complain about is I hated the CoD treatment it got with the 2 weapon limit and regenerative health.