Adam.S said:
To me a race depends on the competition, some 1 week stages have better riders than the Giro and Vuelta has. A monument always has the very best riders for the par course it is raced on. Just GC riders get more fame.
The field is only half of it though. It's about the field competing for victory vs. the field getting base miles. The Tour Down Under draws some pretty good fields, but until the last couple of years it was a training ride with WT points.
Until this year, too, it seemed the ASO was absolutely determined to make the CdD a Tour recce with WT points, so you'd get almost all the Tour's contenders, but next to nobody peaking.
The 9 most important races in the world are the 3 GTs, the 5 monuments and the WC RR. We can debate the order all we like (I think Lombardia is getting a bad rep at the moment, though I do admit the current route lacks a lot of the charm of the previous iteration, and I find Milan-San Remo to be less than enthralling much of the time) but the least prestigious monument is still way more important than the most prestigious non-monument one-day race except maybe the Worlds.