There are obviously many many many adaptions of these stories and when you get into the short stories (all of the ones on this list are novel length) you can find more of the lesser known tales as well. I think having knowledge of the originals as well as updating them is important because it shows us where we come from and the various changes that have been made to get where we are now.
What is your favorite Grimm fairy tale? What is your favorite adaption? How many variants one one story do you think they can possibly have?