Knowing my luck, I’ll post this and some Iranian style Muslim Revolution will break out in Asia tomorrow or something. But the question is fairly open: Why is Iran the only true Islamic Republic?
Khomeini in his writings seems to indicate that the form of government that he proposed for Iran would sweep the globe. Though Islamist figures have made gains throughout the Middle East and Asia, there’s no government that quite rivals Iran with their Western style institutionalized President and legislative houses on one hand, and their religious Coucil of Elders and Mullahs on the other. Why hasn't this governmental form flurished throughout the Islamic world?
First most obviously, Iran is a country that is predominatly made up of Shia Muslims. The Shias' are a minority in most nations throughout the Middle East. Perhaps Khomeini’s conception isn’t the governing vision most Sunni Muslims. Or maybe nationalizing such a government proved far too huge a task for countries with leaders not as rhetorically or organizationally gifted as Khomeini.
History is ripe with examples where new forms of governance (Islamic Republics, Communism) sprung up and was quickly copied as an en-vogue governance. Rarely do the sequels live up the original and are marred by great failings.
Perhaps there aren’t more Khomeini spawned systems because future generations have seen the inherit problems with such a system. Just because it persists in Iran does not mean people are thrilled with the system, which has to rely on brutality just to remain upright. Furthermore, transplanted systems often don’t meet local realities as exemplified by the British electoral systems adopted in Africa after colonization ended.
There’s no guarantee that a pure Iranian system would work anywhere other than the Iran that spawned it.