If economic opportunity is your motivation then the U.S. is a much better place to be than the UK, but if you'd just like to live a normal life with healthcare and a house, the UK is a far better place to be than the U.S for most people. "Economic opportunity" as a motivator is itself a U.S. mindset.
Source: an expat living permanently in the UK.
Meanwhile America is being driven into the ground by Trump and Elon.
An immigrant is one who moves from a poorer country to a richer country. An expat is one who mixes from a richer country to a poorer country.
One cool feature of my definition is that it explains a lot of the cultural subtleties in comparing these groups: how immigrants adopt the local ways much more than expats do (expats retain that touch of superiority) etc etc
On average, every situation is different, this is just my general rule of thumb pattern I've observed.
There is a question how much it destroys other countries too, but the fall of us is pretty much granted.
Subjectively, I visited London twice over the last year and it felt fun and bustling.
I had to wonder why London would rated be above Tokyo and I had my answer immediately.
personally I think #1 is overdoing it even though I live there but probably top 5. Depending what you prioritize.
The first two sentences of the wiki reveal both the British nature of the publication and its focus not on great cities but on measuring how large cities are open to investment and trade from foreign markets.
This is as close to approaching no one’s definitions of a great city as I am aware.