It has to be noted that his films where shot on film, but edited on video. The masters that exist are always going to be 480i until they find the original filmed elements and recreate the edit for HD. This excludes a few projects that were meant to be shown in theaters which were edited on film.
Depending on the way the original negative has been stored (thus effecting the cost of restoring the filmed elements), there is actually more work to be done on the post-Bad Videos. Basically, Thriller, Moonwalker (which includes Smooth Criminal and Leave me alone) and Ghosts are HD ready. They were edited on film for theatrical exhibition. All they have to do (and have already done for moonwalker) is make an HD master of the answer print.
With the OTW-BAD videos all they have to do is find the original filmed elements scan and re-edit them. While it isn't cheep, it isn't nearly as expensive as it used to be. Most of the videos featured straight cutting and in camera effects. Billie Jean would probably be the most time consuming to recreate (because it used a lot of early video effects).
Now with Dangerous up until HIStory (again all footage was edited on video) you have TONS of big budget effects, all of which were created in video for 480i video. Recreating all these effects would be very costly. Scream cost 7 million dollars at the time, all of that work would have to be re-created. Anything digital or comp'd in would have to be recomped. It would be a time consuming and costly process, it is something they should definantly do, and probably will. It's also the reason it hasn't been done yet.
