I don't know if "universally accepted as art" is quite what you're going for either. I think that by saying a masterpiece is accepted as art discredits whatever art form you're trying to place it in - obviously it's art, but it's clearly defined as a great or skillful work within that field, or is widely acclaimed and praised, which would necessitate the existence of that kind of art in the first place (along the lines of a hypothetical syllogism), as it would necessitate art that's not quite at the "masterpiece" level (not necessarily tawdry or hack art, either, but solid examples of the range). Therefore I think by defining that there are masterpieces in any field thus makes a concrete statement that the form is an art to begin with. Since (at least in my views) in all of the fields you've stated there are masterpieces - such as I've given already in literature, but in photography there are masterful photos such as that of the Tank Man photo in Tiananmen Square, or digital art which is such a broadly defined field that you'd have to specify further as there are so many great examples in each discipline (animation, digital paintings, etc, etc).