If we're to believe the well-known lunatic Werner Herzog, he's never actually seen Abel Ferrara's Bad Lieutenant. Supposedly (I guess?) he just liked the premise (and title?) and decided to make his own film about a corrupt, depraved, drugged-up cop and place Nic Cage in the Keitel role and shift it from New York to New Orleans and give it the odd title of Bad Lieutenant: Port of Call New Orleans. Ferrara has said that Herzog can burn in hell.
It's certainly hard to pinpoint many parallels between individual scenes, though at least one is pretty close: Keitel's legendarily perverse exploitation of an underage girl at a traffic stop becomes Cage having his way with a young woman during a traffic stop (while making her boyfriend watch and asking her bizarre questions about whether her parents used to enjoy seeing her in school plays!). If Herzog hasn't seen the original, he's no doubt heard about its major scenes.
Origin stories aside, though, I suppose the film ultimately has to exist on its terms. So, does it work? Well, mostly as a curiousity, I think. While the story itself follows a pretty familiar police-procedural path, the reason we're watching is to see Nic Cage come unhinged! Oh, and he does! The problem with the performance, though, is that audiences have become so accustomed to seeing Cage act bonkers in (generally pretty bad) mainstream films, that it's damn near impossible to figure out if he's giving a real, go-for-broke performance or just indulging in a collection of mannerisms he's cultivated throughout his career (can the answer be: both?).
The film's trailer has developed an immediate cult following, so it's easy to imagine a great deal of the audience (I'm guilty) awaiting the scenes we've been hearing about, such as the imaginary iguana staring contest (set to funky music!) and the breakdancing soul. But don't worry, because there's plenty of other weird shit to enjoy (I swear there seems to be a car-wreck scene shot from the point-of-view of an alligator).
Aside from the general nuttiness factor and Cage's wild performance, the film's other biggest advantage is its setting. Herzog's post-Katrina New Orleans is a place where corruption seems to seep right out of the landscape and into the body (the film recalls the great Chinatown a bit in the way it creates a world that is simply ripe for depravity and exploitation). The film's one potential (arguable) moment of epiphany seem to arise when Cage realizes that sometimes the world can function without such corruption. But that quickly gives way to an ambiguous ending that hinges on whether fish can dream or not.