I don't remember anything prior to the mid-70's but I have a distinct impression that cities everywhere in the western world were much dirtier and crime-ridden in the past (things began to improve around the 1980s, or Rudy Giuliani time).
That's certainly true of the US in general. The standard narrative is that it was driven by "white flight," which in turn reduced investments in urban infrastructure, etc. Like many narratives, there's some truth in it but it doesn't really account for the fact that at least some Western European cities were also dirtier and more crime-ridden than today.
Giuliani was elected mayor in 1993, which did line up pretty well with New York getting cleaned up a lot. However, this was a more general trend even if it didn't apply everywhere (e.g. Detroit).
