I agree with the Empire State Building as being the greatest and most amazingly constructed, but the Chrysler Building would be #2 on my list.
While I grieved deeply for the destruction of the Twin Towers to the Terror events of 9/11 and the loss of life on that day of infamy, the buildings themselves were soulless glass boxes built of inferior material and having no style. I love the grace of the classic stepped Manhattan buildings.
I was just driving through Orlando and I commented to my wife that I love the fact that their newish Tall buildings have some style and very few plain glass boxes.
Jim