The best effect, position yourself as far east in Manhattan as possible. But ensure that when you look west across the avenues you can still see New Jersey. Clear cross streets include 14th, 23rd, 34th. 42nd, 57th, and several streets adjacent to them. The Empire State building and the Chrysler building render 34th street and 42nd streets especially striking vistas.
While we are on the subject, when viewed from all latitudes north of the Tropic of Cancer (23.5 degrees north latitude), the Sun always rises at an angle up and to the right, and sets and an angle down and to the right. That's how you can spot a faked sunrise in a movie: it moves up and to the left. Filmmakers are not typically awake in the morning hours to film an actual sunrise, so they film a sunset instead, and then time-reverse it, thinking nobody will notice.