I never bought Greatest Hits - HIStory Volume I in 2001, because it was just the first half of the HIStory album that I bought in 1995.
I bought Number Ones, because it had One More Chance on it which was good enough to add to my collection. But I didn't buy all the different covers, because that was a rip off like the different coloured Invincible covers.
The Essential Michael Jackson, I couldn't be bothered to by it I already have the songs on it on different albums and singles in various formats.
Visionary: The Viideo Singles, can be seen as a rip off as or a waste of money as I already have all of the singles on vinyl in their original covers and all of the videos. But I thought this was a nice item to add to my collection as the boxset was well designed and it was only about £3-4 a week to buy each single on their release every week. I really like the Visionary Singles boxset so it was worth the money.
King Of Pop album is one I haven't bought yet. It does seem like a huge rip off considering how many greatest hits albums of Michael's have been released over the last 7yrs. I've seen the Australian CD online which has a better album cover and packaging then in the UK, so I might by an import version, but I'm not in a rush.
I can't see the point of Michael releasing more a less the same songs over and over again on different titled greatest hits albums. They are profitable as most have been in the UK top 5 album charts on the week of there release. But I think more albums like The Ultimate Collection with unreleased songs or songs not released as singles like a Best Of should be released as Michael Jackson Compliation whilst he has no new current music released. I would add some of the same songs to my collection if these Greatest Hits albums great albums cover designs, but even the photos on the albums are rehased from albums and past singles. The cover from Greatest Hits - HIStory Volume is originally from the back over of The Jacksons Live album, which was then used in the inside gatefold cover of the 1995 HIStory album on vinyl etc. There are much better ways to exploit Michael's past music, and make it seem like something you haven't owned in the sameway before.