Yes, G7 _power_ has rested on supressing the Third World (backwardness isn't really right--one could say the Vietnamese during the war, for example, had little technological development but plenty of political development.)
But power is not prosperity, which is what I understood the question to be about. (It's at least possible that it's not only India's or Korea's or Iraq's productive capacity that's supressed, but the U.S.'s and Canada's.)
I'm interested in this question as an organizer, and in the U.S., at least, the question is, is my relative comfort as a first world person (if I am) reliant on the elites of my country pillaging the 3rd World? (And the unspoken corollary, is it against my personal interests for that to stop?)
Many leftists in the U.S. answered yes to both and concluded that the U.S. population is therefore too bought off or bought in to expect any serious organizing here against imperialism. I disagree, not on the basis that the Third World isn't oppressed by the First, but that imperialism is not actually the cause of what prosperity there's been for the majority living in the center (rather, peoples' struggles have been). The domestic costs of empire have not been so visible for a while--since Vietnam?--so it's an opportunity to show just how much we're _not_ getting from our elite throwing around their weight, how much we don't actually have in common with them, and just what all this means to democracy at home as Doug said--you know, that little problem, empire or republic.
Jenny Brown