If not for injuries, would Vitali have become an ATG?

This is exactly what I was going to bring up.

Vitali had (has?) a lot of talent, but truthfully who would he have beaten over the past 4 years to secure an all-time legacy? Wladimir is facing a similar problem right now. It's highly doubtful Vitali would have been able to egg Lewis out of retirement, so he'd have the same crop of lackluster opponents Wladimir is forced to fight.

Furthermore, Vitali and Wladimir would not have been sharing all their victims, so Wladimir would have fewer of these "top" fighters on his resume, and Vitali wouldn't have all of them as well. I doubt they'd end up fighting each other, so all we'd have is two brothers who dominated a very weak era in the heavyweight division. That is perhaps novel but not legacy-making.