Grab it From the Bargain Bin
The game definitely doesn't attempt to do anything different. Sure, the graphics are pretty good (even 3 years later), the polish is there, but most of the gameplay is simple. And that's just what I liked about it.
I shot waves of weird-looking enemies, found hidden objects (a carcass produced by a secret ninja chicken), and destroyed big bosses at the end of the level. The game also throws in campy humor during the pre-level cut-scenes, and that helps to establish the game's not-so-serious tone (lame pun intended).
The only thing that I can fault this game for is having occasional hiccups on my 2007 hardware, which did not come from a dip in FPS (I used fraps to determine this); and for ENORMOUSLY long levels. Honestly, this game could be the poster-child for "cut out 25% of each level and it'd be great" games that I often **** about in my blogs. The salt in the wound: when one of the final levels makes you replay two earlier portions.
Overall, I can't fault the game too much, and it's pros definitely outweigh its cons. It's above-average, but with a few annoying issues that drags its score down.