Los Angeles pop: 3,849,378 dens: 8,205
New York pop: 8,274,527 dens: 27,147
Vancouver pop: 578,041 dens: 13,817.6
London pop: 7,556,900 dens: 12,331
The kicker is that these figures obscure the fact that the core of LA just 3 million. In other words, only 1/4 of the people live in the core, and the core is still more spread out than these other cities.
By contrast, half of the people in the NY Metro live in NYC proper. In London, greater than half of the people live in it London proper.
LA's profile is most similar to Vancouver's, which is a city with fewer people in its greater metro area than LA has in its core.
(If you're familiar with Long Island, the metro area in Suffolk would be Suffolk - anything south of the Sunrise Highway up until Westhampton (going up north through Riverhead), and anything east of that boundary)
Similarly, the Boston metro area is often considered to extend out to Worcester and southern New Hampshire, which includes towns like Dunstable (3000 people on land area that's about the size of downtown Boston). But there's a very big difference between a metro area like Boston where most of the people live within a dense urban core and then it drops off to farmland and open space quickly, vs. one like LA where it's medium-density suburbs all the way through.