The 83-year-old pope presided over an anniversary Mass in St. Peter's Square that started at 6 p.m. (noon EDT) — about the same time that white smoke from a Vatican chimney alerted the world a quarter-century ago that a Polish cardinal named Karol Wojtyla had been elected the first non-Italian pontiff in 455 years.
The crowd broke into applause when a weary-looking John Paul was wheeled out to the altar in his throne-like chair, dressed in golden vestments and a bejeweled miter, or bishop's hat, while a choir sang hymns.
In an opening greeting, Cardinal Joseph Ratzinger, a close papal aide, praised the pope for his tireless work over 25 years.
"You turned to young and old, rich and poor, powerful and humble, and always showed, according to the example of Jesus Christ, a particular love for the poor and the defenseless," Ratzinger said.
CBS News Correspondent Charles D'Agata reports thousands of pilgrims of all nationalities surrounded St. Peter's Square for the celebration mass hours before it was to start, with more of the feeling of an international carnival than a religious gathering.
"There are pilgrims here from all over the world and they are just full of faith and full of joy and celebration," agreed CBS News Early Show co-anchor Harry Smith.
Rick Bennett of Lighthouse Point, Fla., has been to the Vatican before, but told CBS News this time was different.
"We've had a lot of fun seeing all the different people from other countries, dressed in their native outfits," he said.
That includes lots of people from Poland, at the Vatican in full force to honor their hometown boy, and representatives from the 301 Roman parishes John Paul has visited. Millions more were expected to watch on television.
Cardinals from around the world gathered in Rome for the festivities and the Mass.
The Vatican was marking the event with great celebration, highlighting the role of John Paul as one of the greatest religious figures of the last century. But the atmosphere in Rome also was bittersweet, because the pope, who suffers from Parkinson's disease, is so clearly ailing.
"He's frail, of course," Washington D.C. Archbishop Theodore McCarrick, who spoke with a pope a week ago, told Smith. "We know he's not this giant that strolled across the pages of history 25 years ago that we all were so fascinated by, but I think his mind is still fine."
Nevertheless, John Paul has continued to defy skeptics by insisting on keeping up with his taxing schedule though he is unable to walk or even stand. He also continues to hold public audiences despite his increasing difficulty speaking, and he has made clear he has no plans to step down.
Eventually, however, McCarrick and the other cardinals — all but five of whom John Paul has appointed — will have to choose his successor.
"Whenever it happens, then I think that the cardinals will want a man who has the same vision, the same understanding of the church, the same understanding of the world as this great pope has had," McCarrick said on The Early Show.
On church doctrine, John Paul has toed a conservative line: abortion, contraception and euthanasia are all banned in the church under John Paul. He ruled out letting priests marry or allowing women to be ordained, and recently endorsed a worldwide campaign to keep same-sex unions from receiving legal recognition.
Such hard-line positions alienated some Catholics and sparked criticism that the Vatican was out of touch with 21st century society. In particular, the church's opposition to condoms has been blamed by some for hurting the fight against AIDS.
"We're living in a world that doesn't accept absolutes...and this man is saying love has to be absolute. You'll have to put your life on the line. You have to decide. You can't bargain with the Lord. You have to be 100 percent," McCarrick said.
A recent poll found that 90 percent of American Catholics approved of the way John Paul had set a moral example, argued for human rights and encouraged democracy. But two-thirds of respondents in the ABC-Washington Post poll said they opposed the church's ban on contraception and married priests, saying the church was out of step with their own lives.
Thursday's ceremony, in which dozens of churchmen were to greet the pope and kiss his ring, was to be followed by the evening Mass to celebrate his election by the College of Cardinals who had gathered 25 years ago to name a successor to Pope John Paul I, who died after only 34 days in the papacy.
On that day, the first plumes of white smoke began pouring out of the Sistine Chapel chimney at 6:18 p.m., the sign that the cardinals had found their next pope. At 6:45 p.m., Cardinal Pericle Felici announced the news from the balcony of St. Peter's Basilica, and at 7:15 John Paul II made his first appearance to the world, asking for patience from Italians because he didn't speak their language perfectly.
Since then, John Paul has had a remarkable tour, helping to bring down communism in eastern Europe by sparking what amounted to a peaceful revolution in his Polish homeland; seeking to heal divisions between Christians and Jews; and working tirelessly for peace in the world, most recently in Iraq.
The Financial Times said Thursday the pope should go down in history as "John Paul the Great."
John Paul is the most-traveled pope ever, visiting 129 different countries in 102 foreign trips. He made more saints than any of his predecessors over the past 500 years combined — a total of 476 — part of his aim to give his sometimes flagging flock more role models.
John Paul also ushered the Vatican into the media age, becoming something of a superstar and drawing cheering crowds wherever he went, particularly among the young. Over the course of his pontificate, more than 16.7 million people by Vatican statistics attended his weekly Wednesday general audiences alone.
"He is truly the global pope," said Cardinal Christoph Schoenborn, the archbishop of Vienna, Austria and a man mentioned as a possible successor to John Paul.