The population of these cities, once and for all!

There are discussions all the time about which is the biggest city. Here are some cities i think it would be nice to know the population ofi have tried to google and i have used emporis to try find the right numbers as well, but they were always different)

Tokyo -8.1mio or 12mio Metro: 33.7mio
Mexico City - 9.8mio M: 27.8mio
New York City - 8.1mio M: 21.8mio
London - 7.1mio M: (11.8mio), (14mio) 18mio
Paris - 2.1mio(why is Paris among the biggest cities??) M: 11.1mio
Moscow - 10.3mio or 11.2mio M: (11.8mio) 13.5mio
Istanbul - 8.8mio or 10.0mio M: 10.0mio or 12.6mio
Mumbai - 11.9mio M: (13mio) 16.3mio
Sao Paulo - 10.6mio or 11mio M: (18.3mio) 20.0mio
Buenos Aires - 2.9mio M: 12.9mio
Rio de Janeiro - 5.9mio M: 11.1mio
Shanghai - 9.1mio M: (13.0mio) 17.1mio
Beijing - 7.7mio M: 14.5mio
Los Angeles - 3.8mio M: 17.5mio
Chicago - 2.8mio M: 9.6mio
Toronto - 2.4mio M: 5.1mio
Sydney - ? M: 4.2mio

So is these numbers correct? LA bigger than Paris? Mumbai, the worlds biggest city? Tokyo the biggest metropolitan area(i think thats right). Don´t know sydneys pop.>