Specifically, I'd like to know which comic books are comic's movie's plots based on. I happen to know that the Daredevil movie is based on Daredevil #181, but I'm curious about mostly Marvel movies. I just want to know if a question like this would be considered on-topic if I asked it.
Asking if a movie is based on some pre-existing material and which works specifically seems to be a totally viable question. While the question touches upon (and ultimately asks for) external non-movie material, it draws a clear connection of that material to the actual film and the answers are (or should be) about that film.
So yes, such questions seem to be on-topic (weird exceptional edge-cases notwithstanding) and probably a large portion of the already existing questions tagged comic-adaptation (or whatever other kinds of adaptations), like this one about the Dark Knight trilogy.