Comment by qayxc

It's much much more complex than that. Climate is only one factor and by far not the most important one. Prosperity and structure of the city plays a much more important role. Singapore is an outlier because it's a rich country on an island the size of a city.

Big cities in Europe are usually surrounded by more rural areas in most of Europe for historical reasons (surrounding farmlands used to feed the city), lessening the need for city parks and greenery since the countryside was surrounding the city. If the city IS the country and even isolated on an island, that's of course not an option.

Another factor is also rooted in history. Like most cities in Europe, Singapore is old, though most of its growth happened in the past 60 years with proper urban planning. Europe's cities on the other hand grew over centuries without any kind of modern urban planning and the pressure of rebuilding quickly after the many devastating wars didn't help either.

Finally there's the issue of money - being one of the richest countries/cities on Earth helps tremendously with building a nice, liveable urban environment compared to some cities struggling to keep basic infrastructure running.