Haven't seen the Babadook, but The Witch was amazing.
I also liked Insidious, but was dissapointed that they gave no credit to HG Wells. It just happens to be that I've read a lot of HG Wells and Insiduous borrows from one of his more obscure short stories called The Stolen Body. Not the whole thing, but a lot of how the ghosts try to posess living human beings bodies and what everything looks like in the realm of the dead. It was all I could think about as I finished watching it the first time. I've re-watched it since and looked for a mention of HG Wells anywhere in the beginning or closing credits, but found nothing. Here is the short story, if you're so inclined to read it and let me know what you think.
http://www.online-literature.com/wellshg/18/