But Alexander was never effectively able to project his power east of the Zagros: witness his long drawn out campaigns out there after Gaugumela.
Yet his achievement was still something that people can marvel at, as he start with much smaller state and smaller population base than Rome.
Alexander's Empire was Mesopotamian based, not Mediterranean.
Who said that it was a Mediterranean-based one?
Furthermore, look how long his state lasted after the man himself died.
Yeah, and Rome wasn't a "one-man empire", like Alexander's, Attila's, or Charlemagne's empires...where the death of its ruler means the collapse of the empire.
Again, it's a comparison that does not work.
Of course it doesn't, Rome was much better in logistics, assimilation, and military flexibility than Macedon.