To me interactivity is the core element here. Platformers can only be interactive. There is nothing about a visual novel which
has to be interactive, in fact the interactivity is usually limited to a few branching paths (although more involved VNs do exist).
I think it is fine to count them as games as long as there is some interactivity, but that obviously puts them at the outer edge of what games are.
To get back to the point, I think a visual novel should be eligible for a literature award, but that is because the interactivity is inherently limited.