The Republican and Democratic ex-presidents defended each other at a Toronto forum on Friday, disappointing some in the crowd of 6,000 who expected a more heated debate.
Mr. Bush said that he never liked it when previous administration officials criticized his government, but said Mr. Clinton was respectful and never did.
Mr. Bush declined to criticize the Obama administration, in contrast to former Vice President Dick Cheney, who has been a vocal critic of the sitting president. Mr. Bush, who wasn't asked about Cheney, said there are "plenty of critics in America."
The two former chief executives did differ on Iraq: Mr. Clinton said U.N. inspectors should have been given more time to conduct the search for weapons of mass destruction and that President Bush should have concentrated on Afghanistan. Mr. Bush disagreed.
"I don't buy the premise that our attention was diverted," Mr. Bush said.
Mr. Bush joked about how much time his father, former President George H.W. Bush, and Clinton spend together. He said his mother, Barbara Bush, "said President Clinton and Father share the stage so much, he's like a son to her."
He said, "So brother, it's good to see you."
Clinton and the elder Bush have worked together to lead fundraising after disasters such as the Southeast Asian tsunami, Hurricane Katrina and last summer's Hurricane Ike.
While both men received polite applause from the audience at Toronto's convention center, a couple hundred protesters demonstrated outside.
The organizers declined to say how much the men were paid for the event, called "A Conversation with Presidents George W. Bush and Bill Clinton." Ticket prices sold for C$200 to C$2,500.
Mr. Bush joked about the speaking fees, which are normally lucrative for former presidents.
"President Clinton and I used to believe in free speech," Mr. Bush said before pausing. "So thanks very much for coming - we are glad you're here."
The two made speeches before taking questions from moderator Frank McKenna, Canada's former ambassador to the United States.
Asked why he didn't stop the killing in the Rwanda genocide when he was president in 1994, Mr. Clinton said he had no excuse or defense.
"It's one of the two or three greatest regrets of my presidency," he said.
Mr. Clinton said the U.S. could have saved 250,000 or 400,000 of the 800,000 people who died had he sent about 20,000 troops. Mr. Bush defended Clinton, saying 20,000 troops could not have been mobilized quickly.
Mr. Clinton praised Mr. Bush for his AIDS initiatives and also hailed the racial and ethnic diversity of his cabinet choices.
Christian Darbyshire and Andy McCreath, partners in tinePublic Inc, organized the event. They hosted Mr. Bush for his first speech since leaving office in March and have also hosted others like former Federal Reserve Chairman Alan Greenspan.
By Associated Press Writer Rob Gillies