iTunes on my Mac shows 138 movies of which 135 have purchase dates. Those 135 were purchases from Apple starting in March 2009.
If I visit those 135 in iTunes some allow me to download, some invite me to purchase again. One old SD movie allowed me to download and that worked on my iPad and showed in the Purchased list after download.
My iPhone seems to show about the same number (though it doesn’t count for me).
My new iPad shows only 24 movies as purchased. Both devices have the same iTunes account. When I view my devices in iTunes (we’re at the 10 device limit) both my iPad and iPhone show up under the same Apple Store Apple ID.
One possibility is that the purchased list on my iPad is only showing HD movies. I can’t tell from iTunes which are HD and which are SD; we almost always buy SD when it is available. Some 3+ GB files are probably HD and they don’t show up.
Something is broken in Apple DRM land. I have a private message into Apple Twitter support and an Apple Discussion post …
Update: The “something that is broken” thing is the user interface. Apple Twitter support pointed me in the right direction.
When I view Movies in TV.app on my iPad there’s a subtle top left drop down called “Library” that on tap shows a hidden filter that defaults to Recently Added.
When I change that to Movies I see them all.
I was fooled by the "See All" link to the right of "Purchased Movies" that displays when the hidden Recently Added filter is active. The “Purchased Movies” heading should really be “Recently Purchased Movies” when viewed in this mode. It shows 4 recently purchased movies, and “See All” shows all recently purchased movies.