Picking up on our discussion of this claim:
The best Hitchcock film was directed by someone else. Charade would not
be as good as it is if Hitchcock had not developed the genre it
epitomises, but Hitchcock could never have created a film so meticulous,
plausible, sensitive, light-footed and funny.
Everyone now seems to agree that "the best Hitchcock film" is, at best, quite a stretch, but what about the broader claim that a [blank] film/book/song might be the work of someone other than [blank]?
There are lots of examples where imitations were better than the original and where plagiarists, from Robin Williams to Shakespeare, put out work superior to what they were imitating, but that's not exactly what we're talking about here.
In this context, the term "Hitchcock film" effectively defines a subgenre (think North by Northwest—with the important caveat that not every film Hitchcock made qualifies as a Hitchcock film by that standard.
Saying someone defines a subgenre is a bit of a left-handed compliment. Obviously, you have to be successful and influential to get there, but that success and influence largely almost always exist within a larger genre. It also suggests that someone else could do it. While Charade is a silly example, it’s not that difficult to imagine someone else theoretically making a better Hitchcock film than Hitchcock. I don’t think you could talk about a Kubrick film in the same way. That said, it is worth noting that countless enormously talented filmmakers—in some cases, arguably more talented than Hitchcock himself—have tried their hands at the subgenre and, as far as I can tell, have all fallen short. François Truffaut, Roman Polanski, and Brian De Palma all come to mind.
What about in other media? An Agatha Christie mystery would certainly qualify as one of these personal-brand subgenres, and we could probably find someone to argue that Ngaio Marsh wrote better Christie books than Christie did (I’m not taking a position on this one, I'm just saying someone might) but it's a difficult point to argue. I would be more than willing to make the case that Dorothy L. Sayers wrote better novels, but here we get into one of the big problems with "better [blank] than [blank]" claims: if you improve too much on the original, at some point, it ceases to be a [blank] work. (Tellingly, if probably unintentionally, when Kenneth Branagh wanted to
make Hercule Poirot more modern and three-dimensional, he did so by
giving him the backstory of Lord Peter Wimsey.) Sleuth also comes to mind. It plays with the conventions of an Agatha Christie story but mainly to subvert them.
If you're good enough to have a subgenre named after you, usually you are good enough to outshine your imitators, but I finally came up with an exception—one so obvious I don't know why it took me so long to think of it. A writer whose very name is a widely used adjective, arguably one of the most influential writers of the 20th century, and yet someone who was routinely outdone at his own game.
H.P. Lovecraft wasn’t a very good writer. There were good, even sometimes great, elements in his stories, but the stories themselves never rose above mildly inept. I went back and reread some Lovecraft, starting with Dagon, and with the exception of a few passages, it took me back to my days teaching junior high English.
We won’t even get into the racism and anti-Semitism.
Lovecraft's writing often comes across as a crude first draft of what could be a very good piece of fiction in the proper hands, which may be why we saw an extraordinary group of talented writers picking up his ideas and running with them—even as he was still writing.
Although the Mythos was not formalized or acknowledged between them,
Lovecraft did correspond, meet in person, and share story elements with
other contemporary writers including Clark Ashton Smith, Robert E. Howard, Robert Bloch, Frank Belknap Long, Henry Kuttner, Henry S. Whitehead, and Fritz Leiber—a group referred to as the "Lovecraft Circle".[16][17][18]
Everyone named in that paragraph was a much better writer than H.P. Lovecraft, and it is because of them—and the others who followed—that his works are better remembered today than The Great God Pan or the stories of Lord Dunsany.