Pfft. "Philip the Great"? Quite the impressive conquest of "Greece", what with the Peloponnesus never being brought into the fold and Sparta standing athwart Philip's ambitions. He totally unified it, too, just as the Athenians had done a century before. And we all know how well that ended. Argread propaganda at its finest!
As for the OP, had he not died fighting the Triballians, Dardanians, and Taulantians in his first year on the throne, Alexander probably would have marched eastward on a Persian adventure. Philip II, after all, had been fitting out an army for that purpose and the Isocrateans of Philip's Greek empire were calling for a crusade to free Ionia from Persian despotism. How well Alexander might have fared requires a lot of inferring, as we don't have many sources on the man, but from what we do have we can guess he was fairly intelligent and fairly charismatic, as well as being endowed with some level of military skill. (His being given command of the Macedonian left at Chaeronea at the age of 16, and his competent handling of it, attest to that.) Who knows what might happen if given the opportunity to actually go on an anabasis to free the rest of the Greek world from the tyranny of Achaemenids? He may well have had the skill to defeat the Persians and secure the freedom of the Greek-speaking peoples of Asia Minor.
Which is interesting enough TL fodder by itself! Without getting into ASBisms of a Greco-Macedonian empire extending from the Nile to the Indus.