Depends where you draw the line. The 5 boroughs alone is about 8M, but the broader metropolitan area is something like 20. (And even beyond that it's still pretty densely populated compared to most places.)

The broader metropolitan is not usually what people consider as NYC. New York state maybe

The broader area is more like that little corner of the state plus half of New Jersey.

New York MSA is 20M, CSA is 23M

NYC = NSW approx then.

Lol and I think Sydney is getting “too busy”