In addition to some of the others mentioned (eg, KATL, KDFW, KMSP etc)...
I'd also like to throw in a plug for a couple of South Carolina airports, namely KGSP and KCHS.
KGSP had been done a couple years back by another developer, but the scenery hasn't aged the best, and it has technical issues that have caused the developer to pull it from the market. I'd happily pay for a more up to date rendition, though I can understand if there isn't great demand or enthusiasm for this particular airport.
KCHS is the busiest airport in South Carolina, with Charleston being a quite popular tourist destination. It also shares runways with Joint Base Charleston and has the Boeing Dreamliner plant on-site. I could see this being a very interesting and in-demand airfield for flight simmers.
I also agree with the sentiment that Africa could use some more "love", as it were...I feel the same about the Indian Subcontinent. Delhi? Kathmandu?