Celebrity, the late John Updike wrote, is a mask that eats into the face of its star. The successful but sad life of Michael Jackson was testament to that. His own personal idiosyncrasies led to his face warping into a freakish public mask unlike any other.

And who really knew the man behind it? He was, for decades, simply Michael, if you were a fan, or Wacko Jacko, if not. Many pop fans today are too young to remember Jackson being black, too young to remember the thrill of first hearing Billie Jean, Don't Stop Till You Get Enough, Thriller or Bad. To some he was a sad and often laughable relic.

And for many, of course, the grimy accusations of child sexual abuse permanently sullied his reputation, as a man, if not as an artist. Yet for many others he remains the touchstone of pop.

As time passes, it will be this Jackson, the artist, his fans hope, that will emerge from behind that mask.

First, of course, Jackson was phenomenally successful. A colossal 65 million people, 13 times the population of Scotland, bought Thriller, his defining album. His other best selling records, the brilliant Off The Wall, Bad, Dangerous and History, are among the best-selling records of all time. He sold 750 million albums in total, at least. He had 13 number one singles in the US. As a pure pop product, he was a phenomenon.

As an artist, his music was primarily danceable. Millions still frug to Billie Jean in clubs and discos across the world. Indeed that song could be among the most effective four minutes of danceable pop ever put to plastic. His root influences were soul and R'n'B, with the technical and electronic aspects of disco - never quite as big in the US as in Europe - thrown in for good measure.

His best songs always had snap and rhythm, from Don't Stop Till You Get Enough, to Beat It, Billie Jean, to later songs such as Scream and Jam. You could dance to his songs, in the bedroom or the disco, but no one could dance as well as Jackson could.

His music was not all fodder for the dance floor. While whenever he tried to sing about "serious" issues it sounded mawkish or vaguely crazy - his earnest squawk of "What about the elephants?" on his gospel influenced anthem Earth Song (which sold more than a million copies in the UK) being a good example - he also sold many copies of love-related ballads, the best of which are sung as duets, notably I Just Can't Stop Loving You from Bad. And all his songs were powered by his voice. His voice was often extraordinary, a sometimes heady mix of soul and shriek, which encompassed everything from human beatboxing to teary-eyed balladry and conveyed a sense of soul which was often missing from his public demeanour.

Jackson was a gifted songwriter, of course. He was no pop puppet singing other people's songs: he wrote nine of the 11 tracks on Bad, for example. But he was also canny and lucky with his collaborators. His work with the producer Quincy Jones produced his strongest material - Off The Wall, Thriller and Bad - but he also tapped the talents of songwriters and producers such as Teddy Riley, R Kelly, and Rodney Jerkins and even worked with the rock guitarists Slash and Eddie Van Halen and the Beatle, Paul McCartney.

His influence, musically, on modern pop is so large, deep and wide it is hard to see a modern pop artist, from Justin Timberlake to Outkast, to boy bands and girl bands, to hip hop and back again, who is not indebted to Jackson's synthesis of pop tune, street beat, hip-hop attitude, rock guitar and gospel.

Timberlake, who emerged from the boy band N'Sync just as Jackson emerged from the Jackson Five, has often been compared to Jackson, but beyond his quintessentially Jacksonian Cry Me A River, his quality songs are thin on the ground. But Jackson does not need individual stars to emulate his song writing and style to prove he was musically important: the entire r'n'b and pop world was transformed by his colossal success.

And that success was universal. He took music that was essentially seen in the US as "black" music - R'n'B, soul - and made it mainstream. Danceable music invaded the Top 10, and has never left. His fans were as fervent in Japan as they were in New York, London or Berlin. His music blurred and removed the boundaries between musical genres in a supreme pop product which millions found impossible to resist.

In retrospect, many have felt that, despite its success, Bad was not a great album, and his output notably declined in quality as his public life became more controversial and disturbing, but Thriller remains perhaps the ultimate cross-generational, universally appealing pop album, and age has not dimmed its qualities.

Jackson's legacy is not only aural, but visual too. His videos in the 1980s, notably the 14-minute video for Thriller directed by John Landis, and Bad, an 18 minute offering directed, remarkably, by Martin Scorsese, changed the language, and length, and cost, of pop videos. These videos were not merely advertising instruments for the songs they contained, the videos became events in themselves.

Yesterday John Sykes, the co-founder of MTV, admitted that Jackson's epics but his station "on the map". "He not only changed music, he changed the culture," he said. Again, like his music, what was once new and exhilarating in his videos later became overblown and risible: the depictions of Jackson saving the world from itself in the Earth Song led to Jarvis Cocker to storm the stage of the Brit awards in 1996.

Over the years, we saw Jackson transform from a king of pop to a dreamy loner, in his world of Peter Pan's Neverland, and finally into to a disturbed and disturbing parody of his former self. But his legacy, his music will live on. And long after the tragedies of his life have passed into memory, the first bars of Billie Jean will still pack any dancefloor.