In one scene of the movie Sin City, you see a road sign. It's the kind that you see when you enter a city or town. It says "Basin City" but the "Ba" have been smudged, leaving "sin City."
Since New Orleans sits in a geographic basin, I guess even slow-thinkers like me can get the association.
So, how much is New Orleans like the movie?
By the way, it was the nastiest movie ever. I wish I could get a mind-scrub to get rid of the stain.