I have thought about this. I just bought some Lovecraft stories. They are right next to a Harry Potter book on my shelf. The dark imagery in Harry Potter reminds me of Lovecraft.

I think the cultists would. Lord Voldemort may have a few loose screws; but his desire for immortality proves that he's far from gone. In Lovecraft, oblivion is more desirable than immortality.

Harry potter reminds me of a mixed match of a lot of other movies and books!

Narnia for example (walking through a wall into another world)
The hobbit (giant spiders in forbiden forests)
Lord of the rings (Golem to Dobby) + (dueling wizards)
Lair of the white worm (the basilisk in the bathroom under the castle)
Worst Witch (witches boarding school + games against other boarding schools)

There has been many books I have read where some things seem to be parts of another book - but Harry Potter seems to take a lot of things from the best ever movies, books, series, and turns them into a complete novel. I personally think the Worse Witch is almost identical to harry potter, apart from the fact there is no orphan with scars in it.