Phillip may have been the innovator who made it possible, but I doubt he was half, hell even a quarter the conqueror Megas Alexandros was...
Darius would have steamrolled his one eyed ass.
Alex on the other hand would have taken his horde straight to China if it weren't for those pesky foothills the Himalayas.
Alexander is overrated. When You look at what he did : he just defeated one crumbling, decadent, ultra divided multicultural failure of an Empire.
Looking at the different battles, the resistance the Persians opposed, compared to their Empire's sheer size, was pathetic. Not just the number, but the quality of the soldier, everything was laughable. A simple Briton Tribe could have conquered half their land.
And in fact, as soon as he started conquering much more organized and stable factions, even small ones, he faced much more difficulties. In the end, when he was about the get crushed by 2 actually powerful Indian empires, his soldiers forced him to retreat, seeing the folly of his plan to cross the Gange.
Alexander had a well organized army at his disposition. In fact, looking at his battles, his main strenght was much more the discipline, logistics and coordination of his army, than his sheer tactical skills.
Alexander is a bit like Napoleon. Bot were dealing in excessiveness, conquering way too much land that an Empire could digest. He is lucky to have died so early, because he would have had to witness the abrupt partition of his Empire : Satraps rebelling, Entire chunks and cities declaring independence, bankruptcy after these endless war, Enemies raiding/invading at the borders... He already had pushed his Old Kingdom to exhaustion, from which it it would never recover.
Alexander was a badass with an iron will. But he is in way as exceptional as some would imagine. What he did, wiser generals would have avoided to do, as it was all short term glory, and no positive outcome would come out of it in the long term.