Timing is everything. Attila was a punk next to Vercengetorix, and Julius Caesar whipped his behind like a puppy peeing on the carpet.
Yes, Vercingetorix was an extremely dangerous rival.
Caesar didn't fare well against him early in the campaign.
And Alesia was a desperate affair.
It is interesting to speculate what might have happened had the Gauls torn a hole in the Roman "doughnut". The Romans were so heavily outnumbered, that had their line been breached and rolled up, they may have lost every legion in Gaul and had a united and powerful Gallic army rolling into Italy. What made Vercingetorix so particularly generous was the imposition of things like order and drill on a barbarian horde. Also, the Gauls weren't really all that barbaric. Settled people, with full agriculture and good military technology. And with a literate chieftain and bardic class. Dangerous and numerous.
They'd never had any order or unity. Administration was their Achilles' heel, and Celts were infamously fractious (still are: look at Ireland!). But Vercingetorix gave them unity, and military organization too.
Very, very dangerous moment for Rome. Could have gone the other way. So could Chalons-sur-Marne, or Tours.
Two out of three went for Gaul/France.
Had Alesia gone the other way, France wouldn't be France in the first place. "Magna Scotia", maybe.