Currywurst and Lindt chocolate

High standard of living, excellent infrastructure (transport, finance, biz, gov), very good education (ETHZ, UZH, ZHAW, etc.), surrounded by amazing nature and landscape, very open and diverse (30% foreigners, all shapes and colors), political stability (don't underestimate this when you're thinking about 2050) and solid governance by direct democracy (ZH/CH)... the list goes on and on.

To not "pollute" this comment with various links the simplest way to get a few reference points is https://en.wikipedia.org/wiki/Z%C3%BCrich

Of course nothing's perfect and there's always room for improvement (obviously), and Zurich is also a place with a very high "transparency of costs" so people pay for most of these benefits (less by taxes - but more by rent, cost of living, etc.) but to keep it short: Historically and with recent and future developments it seems to be a valid candidate for being a good if not best place to live in 2050...