As Matthew Reeve celebrates the release of the new documentary Super/Man: The Christopher Reeve Story, he says he won't forget when his father, Christopher Reeve, appeared at the 1996 Academy Awards.

During the documentary screening at the Sundance Film Festival, Reeve's 44-year-old son looked back on that moment, when his father received a standing ovation during his first public appearance following an equestrian accident a year earlier.

Roughly a year before that appearance, the Superman actor had an accident while riding a horse, leaving him paralyzed from the neck down.

"I remember, I was in London, it was a school night, and we stayed up until three or four in the morning to watch it, and it was absolutely incredible," Matthew told PEOPLE at Sundance.

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"What sticks with me most was after that incredible warm welcome and that very long ovation that he received, his introduction — he followed it up with a wonderful speech about how cinema and movies are at their best when they not only entertain, but [when] they inform and educate and address issues," Matthew said.

"So, that's always stuck with me," he said. "And that's why also I feel like here, at Sundance, that's what they do and that's what they live for."

During that moment in 1996, Christopher was met with a lengthy standing ovation as he appeared on stage in a wheelchair. He opened with a joke, saying he "left New York last September, and I just arrived here this morning."

Christopher quickly turned serious, extolling the virtue of films that challenge viewers to better understand the world. "When I was a kid, my friends and I went to the movies just for fun. But then we saw [Stanley] Kubrick's Dr. Strangelove and started thinking about the madness of nuclear destruction," he said in '96. "Stanley Kramer's The Defiant Ones taught us about race relations, and we began to realize that films could deal with social issues. Now, when you look at films like Platoon and Philadelphia, Lorenzo's Oil, you realize the power of film to present painful but important issues to the public."

Twenty years after the actor's death, the new documentary Super/Man: The Christopher Reeve Story looks back through Reeve's career, as well as his life after the accident. Matthew, along with siblings Alexandra and Will appear in the film and were at Sundance over the weekend to introduce the documentary. The movie also features interviews with Susan Sarandon, Jeff Daniels, Glenn Close, and Whoopi Goldberg.

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