Separately: Your discussion of the definition of "ghost story" seems to call for a citation of Brian Attebery's definition of "fantasy" in Strategies of Fantasy. Instead of drawing a line, he adopted an approach of defining it by zones of increasing centrality, i.e. degree of similarity to a Platonic central point. This can roughly be done by compiling a list of characteristics of that archetype, and checking off which ones the work in question has. Those which have only a few can be thought of as in the outer fringes, as works which only have something in common with the genre.
You can do that with Shakespeare's plays as ghost stories, and I'd agree with your rankings. And I'd note C.S. Lewis's argument that Hamlet doesn't make much sense if you read it as "a man who has to avenge his father"; it works much better as "a man who has been given a task by a ghost," which raises all the existential questions of reliability (how does he know the ghost is telling the truth?) and obligation (what imperative does he have to disrupt a well-run kingdom?) that the other reading doesn't.
As for the detective stories, I consider it quite reasonable to say that some authors (I presume that P.D. James, whom I haven't read, is one) are writing genre detective stories, i.e. are part of the "detective-story community" akin to the SF community, while Poe and Collins predate the existence of this community. This can express itself in the rules about the provision of clues, the hiding of the solution, and fairness to the reader thereby - which the genre fiction writers abide by scrupulously (or they did when I was last aware) but which Conan Doyle, for instance, did not. Nobody is more central to the detective-story canon than he, but his stories don't follow the "rules" of the genre, and therefore there's a line you can draw around certain works which excludes his.
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You can do that with Shakespeare's plays as ghost stories, and I'd agree with your rankings. And I'd note C.S. Lewis's argument that Hamlet doesn't make much sense if you read it as "a man who has to avenge his father"; it works much better as "a man who has been given a task by a ghost," which raises all the existential questions of reliability (how does he know the ghost is telling the truth?) and obligation (what imperative does he have to disrupt a well-run kingdom?) that the other reading doesn't.
As for the detective stories, I consider it quite reasonable to say that some authors (I presume that P.D. James, whom I haven't read, is one) are writing genre detective stories, i.e. are part of the "detective-story community" akin to the SF community, while Poe and Collins predate the existence of this community. This can express itself in the rules about the provision of clues, the hiding of the solution, and fairness to the reader thereby - which the genre fiction writers abide by scrupulously (or they did when I was last aware) but which Conan Doyle, for instance, did not. Nobody is more central to the detective-story canon than he, but his stories don't follow the "rules" of the genre, and therefore there's a line you can draw around certain works which excludes his.