I think this is why I make so much of an effort to experience everything. If it has a neat plot bit in it, I want to read it, even if the rest of it is crap. If it's notable, or it's done by someone who is notable, or it's vaguely related to something which is notable, I want to experience it just to see what went wrong, what went right, and what I can cannibalize from it.
I've got a game idea percolating that came from a truly mediocre Gamecube game called PN-03. I don't know if my idea is good, but it's a damn sight better than that game.
I have no less than five plot ideas that came from the first season of Babylon 5. The first season of B5 is, let's be entirely honest here, crappy. And yet it's still inspired me.
No matter how bad it is, there's usually something to learn.