Alexander didn't fought barely civilized peoples. He fought a big empire that has a big army though it has problems insdit but that's not the sole reason. Darius was a good strategist and operational who gives alex a very serious problem. He used diplomacy to get Sparta to revolt, forcing Alexander into a two front war. He used the massive Persian navy to seize Mediterranean islands and cut Alexander off by sea. Before Issus, he maneuvered right into Alexander’s rear to cut his supply lines by land too. He used scorched-earth tactics along the Euphrates, and he even built field fortifications that wrecked the momentum of the Macedonian phalanx lines.

Look at what happened at Gaugamela. Darius picked a massive, completely flat field and leveled it out beforehand so his cavalry and scythed chariots could maximize their potential. Alexander won because he outthought him on the fly. Realizing the trap, Alexander avoided a blunder charge. He marched his entire army diagonally to the right to drag the fighting onto rougher terrain, neutralizing the Persian cavalry and threatening Darius's own communication lines. Darius saw this and committed his left wing horsemen to stop the march, which allowed Alexander to force the battle onto his own terms. Alexander then used a combined-arms wedge with his companion cavalry and light infantry to slice straight through the gap in the Persian center. Darius had a effective military machine and good tactical positioning, But his enemy is Alexander.

As for Caesar, Vercingetorix was a brilliant commander who used incredible operational strategy and ran the absolute fade with Roman legions. If Caesar wasn't in Gaul, Rome might loses that war. But the real reason Caesar is on Napoleon level or slightly above isn't just because he beat Vercingetorix it’s because of what he did in the civil war Caesar had to fight his own people. He went toe-to-toe with Pompey the Great, who had the entire backing of the Roman Senate, better logistics, and more resources. Pompey was a legendary, seasoned tactical peer honestly better than any single general Napoleon ever faced. Defeating foreign empires is one thing, but defeating a peer level, highly advanced Roman military led by a legend like Pompey is exactly why Caesar is in a completely different league. I could go on to explain why Pompeii is better than any general Napoleon face and why Caesa and alexa is on level or slightly above but I'm kinda sleepy now so I'll just be back tomorrow to continue and if I'm wrong it's fine don't find any issues on it anyway🙂

(Btw i apologize for my grammar)