George Stephanopolous is approaching his 20th year as an anchor on Good Morning America, but it’s not hard for him to pick a favorite moment from the show.

On Monday, Nov. 3, the ABC morning show celebrated its 50th anniversary with anchors past — Diane Sawyer, Charlie Gibson, Joan Lunden and Nancy Dussault — and present — Stephanopolous, Michael Strahan and Robin Roberts — on hand to mark the occasion.

Following the special anniversary broadcast, Stephanopolous, 64, tells PEOPLE which memory from his tenure on the show he looks back on as the “biggest moment.” Looking back, he says, “My favorite moment, if I had to say, was the day that Robin came back from a bone-marrow transplant and said, ‘Good morning, America’ for the first time.”

In August 2012, Roberts, 64, took a leave of absence from her spot as anchor of the show and returned five months later in February 2013 after receiving a bone-marrow transplant to treat her rare blood disorder known as myelodysplastic syndrome.

She was off the air for “184 or 174 days,” Stephanopolous remembers, “but she had a tough road.”

“For her to come back and greet the audience again — and greet all of us again — it was just a proud moment, a joyful moment,” he says now. “It was a fulfilling moment, and it was a toast to the future.”

 

In advance of the 50th anniversary, Stephanopolous reflected on how his journey began at GMA after his tenure as Bill Clinton’s advisor.

“When they first came to me with the idea that I should join Robin as a co-anchor, I said, ‘Are you kidding? That’s not what I do,’ ” he told PEOPLE. “And I said, ‘No.’ We were living in D.C. at the time, and I just didn’t think it was the right fit for me.”

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“But thankfully, the president of ABC News at the time, David Westin, persisted and he was very persuasive and he asked me a second time, I demurred the second time, but the third time, he made a heartfelt and very persuasive pitch, and I said yes,” he continued.

Accepting the job as co-anchor, Stephanopolous said, is “one of the best professional decisions I ever made.”

Good Morning America airs weekdays on ABC. Check local listings.