Not knowing what part of NYC you spent time in, all large and even medium sized metropolitan areas, anything over ~500,000 or so, have better and worse neighborhoods.
We tend to form prejudices based on the part of the city we first encountered. My own personal prejudices are just as biased as anyone else’s, but knowing that doesn’t change them.
I like San Francisco, Tucson, Berlin, Nürnberg, Budapest, Independence, Toronto, Vancouver, Anchorage, Fairbanks, Omaha, Rochester, Seattle …
Dislike Los Angeles, Philadelphia, Paris, Phoenix, DC, Memphis, Sacramento, Miami, Cleveland, Utica, Fayetteville, Trenton …
Mixed feelings on Boston, St. Louis, Atlanta, Kalamazoo, London, NYC, Salt Lake, Buffalo, Montreal …
In general find people to be more polite but less friendly in the south east than in the north east, but again its all first impressions unless you really know a town and all the sections of that town (and nobody ever does) any place could end up on your top or bottom list.