What could be better than an
altruist with
absolute power,
vision, and
intelligence? The benevolent dictatorship is, bar-none, the perfect form of
government. Given that you can maintain it...
Unfortunately, maintaining a benevolent dictatorship is nearly impossible. Once the dictator is overthrown (or dies of natural causes), a malevolent dictator usually steps in, and takes advantage of the heavily centralized power structure that the benevolent dictator left in place. Another poor end can come about if the dictator is too weak to resist the axiom that "power corrupts, absolute power corrupts absolutely". Overall, the possible consequences of enacting a benevolent dictatorship are generally viewed as outweighing the benefits. So they are doomed to happen only as accidents of history...
There are actually several examples of benevolent dictators in history: Katherine the Great of Russia, and Fredrick the Great of Prussia were both, I believe, relatively benevolent dictators. As were a string of emperors in ancient Rome, including the emperor Hadrian and the emperor Claudius.
This is, of course, all predicated on the assumption that the populus is on average too stupid or uninformed to make good decisions about governance. Which I have to admit I agree with. I'm an elitist. Democracy is stable, but it's guaranteed to be mediocre.