Should story adaptations always be the same?

I've heard a lot of negative comments over the last two years of certain books and stories being adapted into films. A lot of the times the plots are different from the original source material and people use that to decide that the films are no good. That isn't always the case though. Let me show you some examples of films adapted from stories that did very well.

From what my friends have told me if they had stuck one-hundred percent true to the book it would not have done as well.

Ah yes, the classic story. True it stayed very true to the original fairy tale. However there were a few things taken out, like the Queen's first two attempts to murder Snow White via a poisoned comb and a poisoned corset. Also in the original story the Queen died when she screamed so loud she broke a blood vessel while in the film she fell to her death off a cliff with a boulder following in pursuit.

Very big differences from the source material here. Elements of mysticism and high fantasy in the film adaptation of the beloved children's book. Nevertheless the film did an outstanding job.

Now you're probably wondering "Wait. This film stayed very true to the books! Why is he posting it here?" Yes it's true that this film stayed very true to the books. However there were some differences between the original novels and the films. The incident involving Tom Bombadil was never featured in the films. Also the encounter with Shelob happened in The Two Towers, not The Return of the King. If films had to stay completely true to the books then these films should've been hated.

Last one. I promise. This film adaptation was definitely a big success, yet it too was very different from the book. There were fifteen dinosaur species in the book and only seven were shown in the film. Also two of the films species were not featured in the first book. There was also a major plot element where the characters see Velociraptors sneaking onto the boat and they try to call in to let the people know what's happening. That was completely scrapped from the film.
One thing we could possibly look at with film adaptations of books and stories is if they capture the spirit of the original tales or not. That was how the author of How to Train Your Dragon, Cressida Cowell, looked at the film of her book. Diana Wynne Jones knew that the adaptation of Howl's Moving Castle, yet she was okay with that. I've been thinking that maybe we go to the movies expecting to see the books. Maybe we shouldn't. There probably comes a time when a story will need to be re-imagined. After all the original fairy tales we grew up with were edited and changed because the original versions could get pretty dark and graphic. I doubt parents would allow children to read or see a Cinderella story where the stepsisters cut off their heels to try and make the slipper fit. Maybe one of the keys to re-imagining a story is to stay true to the spirit it had. The time will come when we will need to re-imagine our stories. If not they will most likely not survive to entertain the next generation.