Think the Ft. Worth to Dallas analogy.
Newark has its own downtown, Performing Arts Center, hotels, universities, Prudential stadium and business district but majority of business and rush hour commute is centered around Manhattan.
Or if you are going out for nightlife:
Newark resident can visit Ironbound, Newark (many restaurants/bars) or take approx. 20 minute train ride into Manhattan.
Manhattan/NYC resident would rarely visit Newark for nightlife except for show (PAC or Prudential Center), airport, education or shopping at nearby factory outlet or IKEA.
Other NJ locations with similar profile - Jersey City, or Hoboken. I would categorize all as shadows of NYC.