That's a weird metric to measure a city by. NYC is a vibrant city whose interestingness is intrinsically tied to the unique, sometimes weird blend of people inhabiting it. But tying this colourfulness to the amount of grime in the subway seems like a strawman to me. NYC isn't what it is because of smelly bums in subway cars, leaking ceilings, "showtime" kids or schizophrenic maniacs wielding knives, all of which feature heavily in the subway.

Secondly, there are plenty of cities with clean, "quality" civic spaces that are also have plenty of weirdness and colourful culture, including Berlin, Paris, Barcelona and Moscow.