Real tough question, I'm not even going to vote.
Too many areas of subjectivity, less knowledge or detail as we go further back in time. We know Roman generals were very good at having those writing about a campaign to also function in essence as the general's PR department. And I am sure the Romans are not alone in this.
And what really defines a great general? Luck? Conquest? Being outnumbered? I'd rather have 4 German WW2 platoons than 8 Italian ones.
Let's look at Alexander for instance. Most commonly he is given recognition as the best general of all time, but I have also seen him to thought of as someone without great tactical sense that single mindedly would just attack, attack, attack. And often, this tactic can be effective, but it does not make one a great tactician.
Some look at Granicus as a failure on the part of the Persian command, looking to oblige his tactics by meeting him in the middle of their river instead of defending the shore with their lines of hoplite infantry and using their cavalry to attack and defend the flanks.
Even the very tactically sound Macedonian army with it's hammer and anvil capability was organized by Philip, not Alexander.
Personally, I think he was a great leader "from the front", brave and inspiring, but perhaps could not see the forest for the trees at times as a tactician, and perhaps a spear thrust away from losing the campaign.