I think I remember the post you mean, although I can't find it. It listed some of the Empires between the Roman and the British which are simply ignored. I've pasted this from Wikipedia which summarizes some of these 'world powers'.
Although the term superpower is a recent one, the word has been retrospectively applied to previous military powers. The oldest superpower on the planet, and one which maintained this at various points in history, were the civilizations in Mesopotamia, with their unrivalled wealth, antiquity and cultural domination of Asia and beyond. The Roman Empire covered most of Europe, North Africa & Asia Minor. Imperial China once had the world's largest navy, a record not broken until early 19th century. The Mongol Empire spanned from southeast Asia to Eastern Europe. In 16th and 17th centuries the Ottoman Empire stretched from the Straits of Gibraltar to the Persian Gulf and challenged the nations of Europe in its advances along its southeastern border. During its Siglo de Oro, the Spanish Empire had possession of Italy, Germany, Portugal, The Netherlands and many colonies in America, Africa, and Asia. After gaining independence from Spain the Dutch Empire were able to establish territories all over the globe. At various times during its history France had the largest military in the world, with colonies in western Africa, North and South America and southeast Asia. At its peak in the late 19th and early 20th centuries, the British Empire covered a quarter of the Earth's land area and comprised a third of its population. It was said "The sun never sets on the British Empire." Not as clearly in this category are nations that gained unquestioned hegemony over a large neighborhood at a time before global travel was a reality. Nations such as ancient Egypt, the Aztec Empire, the Persian Empire, and the short lived Greek/Macedonian empire under Alexander the Great could in one sense be considered early superpowers, at least for a time when an understanding of what is meant by "the world" was much smaller than it is today.
http://en.wikipedia.org/wiki/Superpower#Superpowers_in_history