The 28-year-old earned plaudits for his patience at the crease, with many praising his calmness and clever leadership.
"Williamson has to be New Zealand's greatest ODI player of all time, and an innings like that against South Africa tells you exactly why," Vettori said in a column for the International Cricket Council.
"He's already there now and by the end of his career his record will far exceed anything we've had in the past or present, he really is that good."
Vettori, who is New Zealand's most-capped ODI player and guided the Kiwis to the 2011 World Cup semis, said Williamson's mature approach to batting is what sets him apart from most other batsmen.
"What differentiates him from a lot of batsmen in this day and age is his sole focus is winning the game and he tailors his batting towards that," Vettori added. "The way he understood that situation and got his team across the line was exceptional.
"It's what makes him one of the greatest in the world now and by the end of his career he'll be up there with some of the greats of all time."
New Zealand, who are unbeaten at the tournament and in a strong position to qualify for the semi-finals, next play West Indies in Manchester on Saturday.
(Reporting by Shubham Kalia in Bengaluru, editing by Ed Osmond)
