In terms of world power you have to take into consideration the amount and availablity of nuclear weapons. Also where the country is located which is why some Middle Eastern nations are in fact world powers due to the fact that they have mad supplies of the prescious oil that the entire world needs.
Since many nations have nuclear weapons including: USA, Russia, Pakistan, India, North Korea, blah blah, etc...they have to be in the top 10 based on that fact alone.
Based on what one of Hitler's advisers told the prime minister of Japan before WWII started, "If the United States enters this war they will become the dominant world power in the future." I will end my post with that.