I guess this is about international passengers, not total passengers. Because according to this Dubai is #3 and Hong Kong is #4.
Sao Paulo makes the list. But it's urban area population is twice that of Rio or Buenos Aires. If you cut the amount of traffic for Sao Paulo in half for these other cities then obviously they wouldn't be seeing as much traffic as Moscow.
Sheremetyevo 31.6 m
Domodedovo 30.5 m
Vnukovo 15.82 m
There's also Zhukovsky, new airport opened in 2016, with 4 million declared capacity.
Just Sheremetyevo alone was 40,000,000 in 2017.
Pretty proud since I hardly typed in any wrong ones (did try 3 big s-american cities, rio, sao pãolo and buenos aires, and another in japan, top 3 africa, a couple of europe and berlin. Think that were most of my wrong guessed)