Forget about the origin of the plot. Forget all about the "SS & FF brands." Forget it all. Go enjoy the movie as a movie. Look for plot, character development, interesting dialog, exciting special effects. Don't stay away from a movie just because it does things different than the comics or "changes the brand".
Don't be that guy.
I don't mind changes.
I mind changes that are bad or arbitrary.
There are no other superheroes in the world other than the ones in the movie
I understand that- the Scarlet Witch's probability affecting powers were just one example of gaining the same effect as in the movie without changing a thing about the SS character. (Proteus, from X-Men storylines, would have been another...)
IOW, I'm saying there were ways to do that "power switch" without mucking with the integrity of the SS character.
After all, Reed Richards is constantly pushing the boundaries of super-science in his lab- perhaps one of his
numerous attempts to alleviate the monstrosity of Ben Grim's condition could have gone awry...at the worst possible moment.
But to simply discount the entire movie just because it clashes with the Fantastic Four/Silver Surfer "brand" is an injustice not only to the movie, but to yourself. You are denying
yourself the chance to see what may turn out to be a fairly decent movie.
I really don't think so. IMHO, making needless changes are an injustice to the source material. I see no reason to scale down my critique of a film just because its a "comic book movie."
I already had a problem with the change with Reed Richards no longer being significantly older than his wife Sue- their May-September romance was a defining part of their characters, a solid link between them and other romances of the sci-fi movies of the era in which the FF originated. Eliminating that also excised certain dynamics between the two of them.
The change in LotR that you cited is one that could
possibly be viewed as an improvement over the original source material. While JRRT was a fantastic world builder and linguist, there
are flaws in his writing. His prose could be tighter, for instance, or certain interactions more realistic. Even with that, though, his stuff is rightfully considered to be classic.
But in no way is this randomization of the FF's powers by the SS an improvement.