Let's see:
Greece- Just think of the food-related possibilites. Plus, an ancient Greek dark ride would be cool.
Egypt- I'm thinking mummy-related dark ride. (Possibly on a humerous idea)
Brazil- Just think, Carnivale makes its way to Epcot!
Austrailia- Perhaps a more extreme ride is suitable for this country.
Jamaica- No rides here, just good food, good music, and good times.
Switzerland- Cool architecture.
Russia- More cool architecture.
and the number 8 spot goes to:
Spain- C'mon. Epcot was planning this one from the beginning.
Honerable Mentions: Israel, Puerto Rico, Sweden, India.