As far as KC registrations go, for last year it was from 1 - 5, labrador, cocker, springer, GSD and staffie. There are probably twice as many non registered dogs about, including as you say OP Jack Russells. Huge difference in numbers registered in the top 5 too, 44,000 labs thrugh to 8,000 staffs.
Round here it's border terriers, jack russells, spaniels, labradors and pointers - can you tell I'm in a big shooting area?! Also see a lot of collies around here.
I just researched the top five breeds in NYC, and apparently it's:
Yorkshire terrier
Lab
German Shepherd
Bulldog
French bulldog
I rarely see Shepherds, so I guess they're more of an "outer borough" rather than Manhattan thing. There are also plenty of rescue mixed breeds in the city, Pit Bulls aplenty.