As the gigs wound down on Saturday, organisers turned their thoughts to Wednesday when the leaders of the Group of Eight industrialised nations meet in Scotland to discuss aid to Africa.
Live 8 coordinator Bob Geldof urged 200,000 fans in London's Hyde Park to demand "No more excuses" from the G8.
"Mahatma Gandhi freed a continent, Martin Luther King freed a people, Nelson Mandela freed a country. It does work. They will listen," Geldof said.
He was joined on stage by Paul McCartney, who opened the London gig with a rendition of "Sergeant Pepper's Lonely Hearts Club Band", Bono, Madonna, Elton John and a re-formed Pink Floyd.
Live 8 eclipsed Live Aid 20 years ago, when Geldof pulled off a pop world sensation by gathering dozens of acts to raise more than $100 million for Ethiopian famine victims.
This time, though, he wants change through political pressure, calling for debt forgiveness, a doubling of aid to poor nations and fair trade to allow African countries to compete.
Organisers say up to two billion people will tune in to watch the concerts.
The biggest crowd was in Philadelphia, where hundreds of thousands saw actor Will Smith, P Diddy and Stevie Wonder.
But limited television coverage in the United States could dampen the impact of such an impressive show of people power.
"Mahatma Gandhi freed a continent, Martin Luther King freed a people, Nelson Mandela freed a country. It does work. They will listen"
Live 8 organiser
"America has a sense of disconnect when it comes to Africa or places that are very far away, because many of us, most of us, won't get the opportunity to see those places," said singer Alicia Keys.
Others, like former South African President Nelson Mandela speaking in Johannesburg, were determined to put pressure on rich countries.
"I say to all those leaders, do not look the other way. Do not hesitate. We ask our leaders to demonstrate commitment, not engage in hollow promises. It is within your power to avoid a genocide of humanity."
U2's Bono summed up the message: "We're not asking you to put your hand in your pockets but we are asking people to put their fists in the air."
London's raucous crowd was silent when Geldof replayed Live Aid footage of dying Ethiopians.
Kofi Annan addressed the crowd
during the London concert
After freezing on the image of a girl on the verge of death, the same person, a now healthy Birhan Woldu, was introduced on stage.
If the message was that Live Aid really did make a difference, not everyone was sure Live 8 could do the same.
"I don't think the awareness thing is working," said Sue Kim, a 22-year-old student, in Philadelphia. "There's going to be a lot of drunk people and what are they going to remember?"
There is also concern within Africa that boosting aid to countries may only bolster corrupt governments.
G8 leaders meet on 6-8 July near Edinburgh, where 200,000 demonstrators marched peacefully through the city to back the Make Poverty History campaign.
Tokyo kicked off Live 8 with Icelandic star Bjork, who expressed the despair she felt in the face of Africa's problems.
"I don't think the awareness thing is working. There's going to be a lot of drunk people and what are they going to remember?"
Student in Philadelphia
"I look at the news, I see people starving, I am crying. I'm a total mess," she said.
Live 8 was also staged in the Circus Maximus in Rome and before a crowd of 150,000 in Berlin where most Germans felt it was a good idea even if they had doubts about its impact.
Stonemason Bernd Oppermann said: "I think every little thing helps to raise awareness about poverty no matter how small, and hey, this is the greatest rock concert in the world."
In Barrie, near Toronto, 35,000 people turned out for the musical feast, while France's concert boasted the Chateau de Versailles as its elegant backdrop.
The crowd in Moscow's Red Square was small, perhaps unsurprising in a country where more than a quarter of the population lives below the poverty line.
And in Johannesburg, most of those interviewed among the crowd of 10,000 had never even heard of Geldof, who has been criticised for largely excluding African artists.
Musician Peter Gabriel stepped in with a separate, smaller gig for African performers, and Johannesburg was added to the list of venues, but that has not been enough to prevent Geldof's detractors from accusing him of "cultural apartheid".