I'm sure Rotterdam, London and Chicago are certified marathon courses, but I got to say this:
If any world class person can run 2:05 and 2:15 in Boston and New York, then that's what separates the Men and Women from the Boys and Girls. No one wants to run them bridges and park hills
It took a simple adjustment in New York (5th Avenue straight into 90th street--Mile 23--as opposed to going into the hilly park at 102nd) to break Juma Ikanga's 10+ year old 2:08:01 (set in 1988).
I ran New York in 1993 (3:12:07), and had I been given the benefit of that adjustment, I might have qualified for Boston. What the heck! Looks like a lot of comments on this. Peace.