Some goofball upthread described Chicago as "not exactly a rural hole". Absurd and kills any credibility poster might have had otherwise. Chicago is a massive, beautiful and historic city, one of the most important in the world on multiple levels. The race is fast, exquisitely organized and executed, has massive fields, huge crowds of spectators, I could go on and on. All of these same aspects apply to New York and Boston as well. The idea that any of them should be replaced is, frankly, stupid.
The only reason some of the other "upstart" Euro or Asian races offer more prize money is because the HAVE TO because they are not on the level of the WMM, several of which also served as some of the first, most important "legacy" marathons in the world. It's annoying that some secondary Euro race would be considered to take the place of one of these biggies because some (probably dirty money Saudi or the like) Daddy Warbucks throws money at prizes.
Marathon aspects that truly matter include the course, the field size, excitement/participation of residents, history, logistics, the city itself as a destination, with elites, records and prize money coming AFTER the other aspects.
I've been to the Paris race, one of the races noted by another poster, and it is (at best) somewhat adequately supported by the city and locals. Paris is one of the best cities in the world to visit but the Paris Marathon is absolutely NOT even close to being on the level of any of the American races in the WMM. Not even close.