I see you already tried all the players you could.
That said, I take advantage of my backup rights to make a duplicate of what I want to keep around with DVDFab noted at http://lifehacker.com/380702/five-best-dvd-ripping-tools
I have the movie Waterworld, is a dual layer disc. Always worked fine, tried recently and no computer or player will not read disc at all. Even players I used to use, new players, new laptops anything. Disc is clean and no scratches. Any thoughts before I trash the movie and buy another one?