Living here, I can unequivocally state that if Allende had stayed in power, the Communists would STILL BE HERE. Chile is very much like an island, so the parallels with Cuba are very strong.
Pinochet was no saint, and he overstayed his welcome. If he had left power after 5 or 10 years, he would be wildly popular today (as opposed to just wildly popular with a significant fraction of the population)...
He did, however, leave power without a fight, albeit reluctantly -- Castro and Chavez are the real dictators, and they will never leave power on their own.