[Summary: The writer wonders at how the Stormlands could compare in any way with the other major regions, given its lack of cities, it's seemingly-average lands, and so on.]

Well, you're right that there are no major cities in the stormlands, but that doesn't necessarily mean the lands are poor. Cape Wrath, the rainwood, and the kingswood are all fertile enough, albeit somewhat rainy.

As for the marches, the marcher lords were for thousands of years the first line of defense against Dornish incursions, so they had a very strong martial tradition. Some strong castles, too. They had to be.