I love London's fashion, no one really cares what you're wearing so whenever you go there you want to be more daring fashion wise. I love Paris's fashion because of its simplicity, it's very sober. I'm also fond of Scandinavian simple aesthetics
NY is cool, but I feel like most of the people who dress well there are very inspired by Eurpopeans. I heard Korean and Japanese are great too

The style of a city is not given only by how people dress y'all.

It's architecture, streets, views, culture and overall vibe play such an important role in that. I'm sure Malibu is full of glamorous dressed people but you wouldn't call it the most stylish place on Earth.

Italy in general is definitely the country where the people are well dressed, however Paris when it comes to fashion and elegance (people) is the best in my experience, but I don't know about the rest of France.
I guess it depends what do you consider 'stylish', Milan is full of people who dress Gucci, Prada, Moschino and high fashion italian (or foreign) brands, people in Italy are well dressed but it's about the brands most of the time and you often see people with all the same things depending on the trends (that we also created).
In Paris there are a lot of elegant people but less "brands" in plain sight.

London is more about a personal style, from punk-rock to Burberry trenchs.

Berlin now is more about this 'punk-skinhead-80's-crusing clubs' that is becoming always more popular in the gay scene.