Two major 18th century creations were highly successful: Washington and St. Petersburg. (The latter is not the capital anymore, but remains the cultural center of European Russia. Vladimir Putin is from there, which hasn't hurt its standing.)
Washington D.C. seems to have fulfilled its goal as a uniting center of the early USA. Having the capital in New York City would certainly be more convenient for Donald Trump's commute... But I suspect that being so removed from the political epicenter would have made the Southern states secede in the early 19th century, and North America would look rather different today.
Major artificial capitals founded since 1900 are Brasília and Canberra, but they look more like Naypidaw than St. Petersburg -- administrative centers with little real metropolitan life.