I recently watched American Gangster (2007,R).  From ScreenIt!:

An honest to a fault cop tries to catch a Harlem drug lord who's directly importing and selling heroin, thus becoming a legend in his own right.

It was weird because I found myself pulling for the murderous drug dealer rather than the honest cop.  Such is the magic of Denzel.  I liked the film. 

I give it 4 out of 5.