Michael Jackson sold more singles and far more albums despite releasing fewer than Madonna. His fame and success is entirely universal - he is critically and commercially successful in virtually every single market in the world. He retains the record (by a landslide) for biggest era of all time in music. He was successful in the 60s, 70s, 80s, 90s, 00s and even in death in the 10s.
Last year (2014) - XSCAPE was the most lucrative release by Sony Music
(source). That will show you how big Michael is. In death he continues to be more successful than almost all current acts year-on-year.
Madonna is insanely successful, but she herselfs knows she isn't on Michael's level as per her 2009 VMAs eulogy about him
