"He is a legend and I love his message to the world," Obi, a 19-year-old student said outside the O2 Arena in south London. "I've been hoping that he would perform live again."
The shows are scheduled to kick off in July and stretch into February. The pop singer has said the series, entitled "This is It," will be his last in the British capital.
After 360,000 advance tickets sold out earlier this week, roughly 500,000 tickets were made available Friday, organizers said. Hundreds of people waited outside the arena for the chance to buy them.
"I have come 150 miles just for this," said Lee Middleton, a 34-year-old construction worker from Liverpool, in northwest England. "We have made some very interesting friends waiting in line. ... People were singing his songs and dancing."
Tickets were priced between 50 pounds and 75 pounds ($70 and $105) - but some were went for hundreds of pounds (dollars) on internet auction sites.
While Jackson has said the shows will be his last in London, there has been speculation they could be part of a world tour. Jackson, who has sold more than 750 million albums and won 13 Grammys, hasn't undertaken a a major tour since 1997 or released an album of new material since 2001.
The 50-year-old singer has been seen in public infrequently since he was acquitted of child molestation in California in 2005. He has struggled to pay his debts, and was forced last year to give up the deed to Neverland, his 2,500-acre (1,000-hectare) ranch and miniature amusement park in California.