Jackson started entertaining as part of The Jackson 5 when he was only 11 years. However, most people associate the height of his popularity with the 1980s. While most people say that he was a singer, I emphasize that he was an entertainer. Jackson sang, danced and played several instruments.
Jackson's list of achievements is long. It includes 13 Grammies, 13 number one singles and many other music industry related awards. Despite Jackson's accomplishments, his legacy will remain mixed. Some people associate him with the strange behavior in his later years. Jackson was famous for veiling his children while they were out in public, having an ever changing appearance and being suspected of molestation.
Regardless of his personal life, Jackson created great wealth for many people. While I did not take the time to aggregate all the sales attributed to Jackson's work, I can assure it is large. I also cannot aggregate the joy he brought many above and beyond just monetary wealth. Today we honor Michael Jackson for using his private property to create wealth.
Wikipedia: List of best-selling albums
A Video of Michael Jackson Moonwalking: