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The 1984 women’s gymnastics champion Mary Lou Retton – nicknamed “America’s Sweetheart” after she became the first U.S. woman to win the individual all-around Olympic gold medal and often considered the greatest American gymnast of all time – says Simone Biles is better.

Hands down.

“I say it over and over,” Retton, 48, tells PEOPLE. “She is the greatest gymnast ever, I really do think that.”

In fact, Retton is so in awe of her power and strength, she believes the 4-foot-8, four-time Olympic medalist could compete in the men’s competition – and win.

“We have a running joke that she’s so strong she should have to compete with the men,” the former gymnast says. “She’s that strong.”

Biles has already picked up the individual all-around gold medal, team all-around gold medal, vault gold medal and beam bronze medal at the 2016 Rio Olympics. She has the chance to score a fifth medal in the floor exercise on Tuesday.

“She’s a special athlete, very unique with a God-given talent that you don’t teach. Her coach, Aimee, is great in improving upon that, but it’s something that she was born with,” Retton says of Biles and coach Aimee Boorman. “She’s just the best gymnast I’ve ever seen in my life and I think a lot of us as athletes and even Olympic champions say the same thing.”

Retton explains that gymnastics is evolving into a strong, athletic, explosive sport, which makes powerhouse competitors like Biles so much fun to watch.

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“Back in my generation, it was slender, pixie, little gymnasts with the pony tails and bows and in walked me in Los Angeles with short hair and this big athletic body with thunder thighs – that’s what they used to call me – and the sport had never seen anybody like me,” she says of the 1984 Games. “Fast forward to now, to 2016, and the women look like I did. You have to be strong since the sport has evolved. It’s so exciting to watch.”

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But Retton says it’s hard to compare the routines she performed over three decades ago to the ones that Biles and the other members of the 2016 team – Gabby Douglas, Aly Raisman, Laurie Hernandez and Madison Kocian – do today.

“Because it’s a completely different sport with better equipment and more spring, literally the vault is a different event, we used to vault on a horse!” Retton, a Nature’s Bounty “Dear Future Me” spokesperson, says. “Our floor was barely a spring floor and now it’s very forgiving with a lot of spring, it’s almost like a trampoline, which is why they can do all that major stuff.”

She adds, “It’s so difficult. I say to myself every four years, ‘This is it, we’re at the limit. We can’t do anything more difficult.’ And then walks in Simone Biles and she just blows your mind.”

The U.S. women’s gymnastics team will compete for the last time in Rio on Tuesday, with Biles and Raisman facing off in the floor-exercise final.

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