Also called an enlightened despot; In the Eastern -Chinese Legalism tradition- a 明君 "míngjūn". There have been instances of them throughout history. But like you said, the problem is usually what happens once the ruler is gone. It's never a (long-term) good idea to have the success of a group dependant on a single person. A political system that produces mediocre-but-stable success (over several generations) seems preferable to one that produces a superior-but-brief success.