Perfectly ethical:
-
Content that is Inaccessible legally such as old games, abandonware, delisted media, banned stuff etc.
-
Digital copies of physical content you own
-
Digital Content that you already own such as ebooks or movies, but are restricted access due to DRM or single-copy rules or other dumb stuff. If I paid for something I should have the right to access it however I want (as long as I don't distribute it)
Gray Area:
- Pirating work that benefits a publisher but not the creator. Movies, Shows, and Songs released by studios that exploited the creators of that material and not giving them a cent. This includes scientific work and research.