Alexanders empire fell immediatly after he died. What kind of general could permit such a thing?
A good general builds his empire to last for centuries. None of that was demonstrated by any of the other choices.
Also, the Romans influenced the world with their domination of it and this influence has no equal by the standards from any other of the choices.
Also, the Romans had to fight a greater share of enemies for a longer time and won.
The influence on ancient warfare is second to none. If the Greeks and Roman legions would have ever net in battle it would have been a disaster for Greece.
If i had to pick another general it would be Kubli Khan who understood total war but too failed to build a systematic empire to tie together the territories of the empire.
Only the Romans of all civilizations created a better place and an enviroment that connected its people on many levels. Roads, Aqueducts, Trade, irrigation, language, Law, technology all developed from the foundations of Rome.
Alexander was not even better than hannibal and the latter was destroyed by Rome.