Paris is a marvel for its density and well-planned routes. But some of the lines are more like underground light rail compared to e.g. the Lexington line, which on its own carries like 1/3 of the passengers of Paris or London.
The London Tube trains I've been on felt like a subway for midgets compared to the 10-foot wide BMT trains. They stop running at night. One of the only times I've missed a flight was due to a London Tube delay.
The new Chinese subways really put the US to shame, quiet, double glass doors, video screens everywhere, cell phones work everywhere, very cheap, very dense and very crowded.
The NY subway is pretty reliable and fast. Apps like Moovit and Citymapper make it pretty easy to get where you want as quickly as possible. Train Time coverage and wifi coverage could be better, the latter is improving. It could be nicer but all I can say is if you think the New York subway is bad now, you should have tried it in the 70s.
Edit: I'd add that an Oyster-type payment system would be nice. Also, a couple of MTA alumni have led systems in London, Hong Kong, Toronto, other cities, so NY is probably not at the very bottom in best practices. Bottom line is you can get anywhere quickly and reliably at all hours, if not always in luxurious style, and you don't need a car to live here. So I'll take it, until your driverless taxi can deal with NY traffic and get there faster.