I'm not saying that review sites are the be-all/end-all, especially places like Gamespot or IGN. But when sites like that -- places where you can basically BUY a positive review -- give you a 3, your game is in trouble.
Now, some of that may be a reaction to expectations that weren't met. Some of it may be the conundrum of a generation of gamers who played and loved Duke 15 years ago when they were themselves 15, finding out that...SURPRISE! they aren't 15 anymore and 15-year-old humor doesn't quite do it. Although I still think that the issue is less one of style and more one of balance.
From the sound of it, balance is the critical problem for the whole game. Balance of elements (new FPS vs. old school -- like, why the f*** is Duke only carrying two weapons?!), balance of level design (too much platforming, not enough ass kicking), and balance of humor (too much lockerroom humor, not enough ass kicking).
DN3D (also available on XBLA), had SOME humor, but it wasn't non-stop and it wasn't always forced. And while you did have some platforming, most of the game was about killin' dudes and blowin' s**t up. And the multiplayer did some really entertaining things with fun weapons like pipebombs and laser trip mines, and teleporters that you could shoot rockets through (I remember the first time I scared the hell out of a friend of mine with that one). But it was, overall, well balanced.
It sounds like this one fails in how it balances these aspects and tends to go too much in one direction and not enough in another.