Of course Plato thought philosophers were the fairest, smartest and most just; he was a philosopher! Lenin fancied himself a philosopher king. It took 2400 years from Plato's writing, but the world finally saw a real live philosopher king, and it wasn't pretty. One thoughtful commentary I've come across recently in regards to the Bolsheviks is that they didn't realize until it was too late that dreaming up policy and governing were not at all the same thing (something I think a lot of the so called think tanks in this country fail to realize, as well). Unfortunately, we also have seen unchecked "democratic" presidents. Robert Mugabe comes to mind, as does Chavez. It seems to be a general rule that when power is too entrenched that corruption takes root. The Chinese seem to be building an interesting government. I despise their views of free expression and environmental regulation (among other terrible policies), but they certainly make one wonder if state capitalism with one party that changes leadership periodically can, in principle, succeed. In this system, one man can't get too powerful, and broad policy initiatives can be executed across several administrations. They are far from perfect (and I don't want anyone to read this as a an endorsement of the Chinese government), but I think we can at least learn something from their system.
In regards to Plato, I don't think he had someone like Lenin in mind. From what I remember of The Republic he envisioned that philosopher-kings would be trained from an early age for rule and that one philosopher-king would be in charge at a time (it would be a collective rule). Of course, this is problematic, as any system seems to be. Your points about the Chinese system are thought-provoking. It will be interesting to see if they change their environmental and human rights positions when they have "caught up" to the developed world in terms of an average citizens living standards. Right now they are simply putting economic growth over any form of rights you can think of.