I am of course biased towards the city in which I live: Sydney, Australia.
I haven't lived in a lot of cities, but I will mention those I have, and some of those I've visited. London, UK. Port Said and Suez, Egypt, Aden in Yeman, Columbo, Sri Lanka. Also Perth, Adelaide, Melbourne and Brisbane in Australia. Auckland and Wellington in New Zealand. So, you can see, I haven't visited any of the reputably great cities of the USA, Europe, Asia or South America.
I have not counted all those smaller places which technically classify as cities, for examples such as Ballarat, Bendigo, Tamworth, et cetera in Australia, or Nelson in New Zealand. Some of these are terrrific places in which to live.
Still I stand by my choice of my own home city, Sydney. It has been rated more than once among the top two or three places in the world as 'the best place to live,' and I believe this is true.