The 70-year-old boxing legend is still a hardcore fan of the sport -- and while he's super impressed with Wilder's run, he's simply not ready to put Deontay in the pantheon with the all-time greats.

"He’s good but he hasn’t approached Joe Louis, Joe Frazier, Mike Tyson. No, he hasn’t approached that kind of recognition yet. No way," Foreman says.

Despite big wins over guys like Luis Ortiz and Dominic Breazeale, Foreman says Wilder still needs a signature win over a top-tier opponent to get the respect he craves.

"For me, he has to have a performance like Mike Tyson did over Trevor Berbick. Boy, when I saw that, I was down visiting Vegas, and I thought, ‘This guy is a nightmare!'"

In case you need a refresher, Tyson's 1986 victory over Berbick is one of the most violent EVER -- he dominated the WBC heavyweight champ for 2 rounds before finally putting him down.

Foreman says Wilder definitely has all-time great potential ... but he's "gotta fight more title defenses and especially no rematches. Rematches don’t count. Unless they’ve beaten you or something, ya know. Rematches don’t count!"

There is one exception ... Tyson Fury. George can't wait for that rematch!