The trouble with Caesar is that the only record we have of his Gaelic campaigns are Caesar’s own commentaries, which are generally considered to be very self serving. You can’t deny, though, that he did ultimately prevail. Much the same with his civil war commentaries. I still put him in the top 5 based on his results, but I would need some contemporary, third party corroboration of his battles to put him at number 1.
The only corroboration likely to become available is from archaeology; by the same standard, everything attributed to Alexander the Great may or may not have happened, since the contemporary sources haven't survived other than by paraphrase from perhaps a primary source (or not) by authors over a century after his death. So I have to disagree.
The record on Hannibal is pretty thin, and none of it from Carthaginian sources (apparently the later burning the city to the ground put a damper on recordkeeping), but he's given props for Cannae; the truth is, he managed to stay a step ahead of Roman forces, and remained a mobile threat (in the form of a large gang of highwaymen) in Italy for 16 years -- but he didn't conguer any more of Italian territory than was needed at the moment for his camp. Overall, he was a miserable failure, wound up accomplishing nothing but pissing off the Romans, handing his hometown the first of a series of defeats, fled into exile, committed suicide, and doesn't belong even on a top 100 list of commanders (ancient, or all-time).