Okay first we gotta see what each region actually has. I'm gonna only count countries where a significant fraction of the area is included (so no including Italy in D or A or France in H). With that in mind,
A: French, Germany, British Isles.
B: Central, Northern and Eastern Europe, Italy, Russia.
C: Balkans, some Eastern Europe, Italy, Russia, northern half of Central Asia, Caucasus, Turkey if we're being generous, China, Japan and (North) Korea.
D: Middle East (sans Egypt), Indian Peninsula, China, Southeast Asia and East Asia
E: Some Arabian Peninsula, eastern North Africa, sub-Saharan Africa
F: Most of South America, western North Africa, West Africa
G: Some South America, Central America, USAmerica, Spain
H: Spain and USAmerica

Some are obviously stronger than others stares at D and G, but wow this is more even than I expected. A gets hard carried by France, B gets Italy and Eastern Europe, C gets (some of) that and also Armenia and East Asia, E gets hard carried by Egypt (sorry for the whole rest of Africa, y'all need better PR), F is the birthplace of the potato and while H is just a subset of G it's a pretty decent one. Without further ado, here's my tier list:

S: D, G, C
A: A, B, E, F
B: H