Yeah, been to NYC twice. The first time I didn't get it. 2nd time I had learnt from my first time, and loved it. Met plenty of friendly decent people.
Been to LA twice, disliked it both times. In total I've been to 42 of the 50 States, generally loved all of them especially when I could get out of the cities into smaller town and countryside.
As for the rest of the world my least favourite have been Sao Paulo & Rio in Brazil (crime-ridden dangerous places), Cape Town (same reason, but saved by the sheer number of unofficial police and security guards). Best cities are generally in Asia, plus Sydney & Melbourne.