Modern philosophy courses tend to give equal weight to Aristotle and Plato (with a side order of Socrates), but for most of Western history the only pre-Christian philosopher that anyone cared about was Aristotle, who was often simply referred to as "The Philosopher". Plato was largely ignored and forgotten until there was a burst of scholarly interest in him in the 19th century.
Source: some random thing I read online somewhere; I might be wrong in the details.
