I said dense, not populous. Density incorporates the area you're settled in.
You can see in those charts that both nyc and london had peak density in 1950, as their populations declined after that point, while their area didn't increased. They both reversed that trend around 1990.
NYC has a much higher density than london though: 27,751/sq mi vs. 14,670/sq mi
This was probably roughly accurate in relative terms around 1950 as well, as NYC and London had similar populations in different areas back then.
Singapore increased its density consistently and greatly in the same time period.
Nope. Even after a massive population increase in the last ten years of the 19th century, New York was still only half as populous as London in 1900:
https://en.wikipedia.org/wiki/Demographics_of_New_York_City
https://en.wikipedia.org/wiki/Demography_of_London