If I may jump in here as a former NYC resident: I've always recommended that anyone who wants to visit the ESB try to time your visit to just BEFORE sunset, while it's still light enough to see things in at least some kind of light. Then stick around if you can for a little while longer and get to see the "glittering city lights" at night.

Lots of people say to just come after sunset, but then you don't get to see the actual city around.