The close reason for lists of work or recommendations reads as follows:
Requests for lists of works or recommendations are off-topic as they do not fit our questions and answers format. Feel free to ask about people's favorites in chat.
It is my understanding that this close reason arose because it tends to allow answers that can all have equal value.
Recently, this question was asked, closed, and reopened. (Full disclosure: I was the one who cast the initial close vote.)
To me this falls under the list/recommended close reason, but a comment was made the because there are only a limited number of works in the series that it should not be considered as such. A good answer probably could list all the works, but that can be said about any list question given enough time and research. The only thing that might change the circumstance is that the request is for a single defined universe. However, answers that are incomplete or give single works that match the criteria would still be equally valid.
So does the size of list matter when determining whether to close these questions?