Painkiller was such a boring and shallow game, I don't even know where to start. Bulletstorm is basically the same thing, same lame "Yo let's do crazy **** and stuff" approach plus you can kick guys in the nuts and receive XP point for it.
Woooooooooooooooooooooooowwwww!
Seriously, when it comes to really compelling FPS experienes that are worth my time, I go shop at Valve.