The BEA publishes GDP/capita for the 50 U.S. states and Wendell Cox just published GDP/capita for the world's 116 major metro areas (those in Western Europe, North America, Japan and Australasia).
The latter comparison adds boundary definition issues to all of the GDP/capita accounting and conceptual disputes. And the smaller the geographic unit, the bigger the difficulty. And international comparisons add exchange rate noise and many other problems.
So, as we do with all data, we hold our noses and jump in. Cities (actually metro areas) are engines of growth because they can be hospitable to entrepreneurial success. Wendell's rankings are a rough measure of all this. The top 25 metros are in the U.S.; Paris is number 26; Naples is last.
It's a nice start.