This is when the Shah was toppled. The Ayatollah Khomeini led the revolution and therefore was able to install a new constitution which allows for some Democracy. Egypt, and the other Arab states are just slower moving. And since the Muslim Brothers did not lead the revolution, they will have a harder time coming up with a constitutional system that will embody their religio-political views but also allow for some democracy. I hope they are successful, but this is not a sure thing.
Yemen's Houthi rebels commit to peace plan in letter to UN chief, BBC reports (Haaretz)
from the article: Muslim Brotherhood lawmaker: Arab Spring headed to Iran