While he clearly was both a renowned philosopher and a succesful emperor, I'm not sure he would be to Plato's liking. Plato seems to favor rather radical social changes and a leader who would use his wisdom to lead his people into a spectacular transformation. Leaders who more come to mind for me like that are Gandhi, Mandela and Lenin. Sure they're not as famous thinkers as Marcus Aurelius, but they did lead their peoples into a radical change with an erudite kind of charisma and a powerful idea.