Alexander the Great founded many Alexandrias. Following his example, the Diadochi and the Epigoni did the same: Antigonia, Demetria, Lysimachia, Seleucia, Antiochia, Cassandreia...
This trend seems to have started with Philip II of Macedon and Philippi:
Philippi was established by Thasian colonists in 360/359 BC with the name Credides. In 356 BC Philip II of Macedon, conquered the city and renamed it to Philippi.
Was there any city named after a real person before the rise of Macedon?
Places taking its name from a legendary or mythological character (Byzantium, Heraclea, etc) are discarded.
Question was inspired by this:
At this time Antigonus was tarrying in upper Syria, founding a city on the Orontes River, which he called Antigonia after himself. (...) It happened, however, that the city did not survive very long, for Seleucus dismantled it and transported it to the city which he founded and called Seleucia after himself.