1. New York, NY, USA
2. New Orleans, LA, USA
3. San Diego, CA, USA
4. Sydney, NSW, AUS
5 (tie). Chicago, IL, USA
Philadelphia, PA, USA
Obviously need to get around the world a little more, but those are the 5 best that I've been to.
EDIT: I'll add that it is quite the testament to how great America can be and operate in a proper urban environment. Our cities are truly quite amazing.
No, they really aren't. The sister cities pairings between European and US cities always manages to highlight the gross deficiencies of the latter. Examples:
Bologna -> St Louis
Gdansk -> Cleveland (ouch)
Rotterdam -> Baltimore (I don't know how it's possible -- one of Europe's worst cities still is better
than its US sister city)
And those are our historical cities that could regain their place with stronger economies and better governance. This pairing, however, is just embarrassing:
Toulouse -> Atlanta (France's prettiest town tied with -- Atlanta)
and they get worse from there.
The US wages urban warfare against its own cities.
Oh, to answer the question: (1) Berlin (2) New Orleans (3) Washington DC (4) Chicago (5) Paris. All of the other "cities" I have been to were the likes of "Dallas" and such.