UK - good chocolates (Cadbury, Tonnick's caramel), hard candies in tins
France - France makes really good hard candies, particularly flower flavored ones, but I don't remember ever seeing them at Epcot. They may have some in the Les Halles gift shop. If they do, I must have been too tempted by the pastries to notice.
Japan - excellent gummies, really interesting flavors of Kit Kats, like green tea, good hard candies, like green tea
Italy - I haven't bought any candy there, but I think they sell Perugina chocolates, which are good, particulary the Baci (kisses).
Germany - anything from Karamel Kuche
Norway - Swedish Fish

DS loves these
China - I think they have the white milk caramels with the white rabbit on the rice paper edible wrapper. They are ok. They might have some ginger candy.
I guess I tend to focus on the pastries and desserts, since many of the candies I have seen in Epcot can be purchased at World Market or my local gourmet grocery store. However, Japan has a really huge unique selection that I haven't found at home.