Chances are good that before your comic book adaptation ever hits the silver screen, a fair number of the target demographic have already written it off as a loss.
Frustrating? You bet it is--especially when you see some of the reasons they're all worked up.
It's one thing to watch a trailer and think the film just doesn't look good. (I do that every time there's an Adam Sandler movie, and I won't hold it against anybody who does.) But when you look at the creative process for these films, it's clear that sometimes fans are just convinced that a movie won't work before it ever begins principal photography.
"You gave me what I asked for! I just KNOW you'll screw it up!"
There were a number of reasons put forth, including that it was an insult to Wonder Woman that Superman and Batman were getting "yet another" chance at the big screen before she ever did, that it was an indictment of DC and Warner Bros. that they hadn't figured out how to use the character and that--this one I remember specifically because it came into play later--she deserved a chance to turn this World's Finest film into a Trinity story.
Of course, as soon as she was announced as appearing in Batman vs. Superman, it began: three characters was a sign of impending doom, because clearly Warners doesn't know what they're doing; the character is being disrespected because they shoehorned her into a World's Finest movie; why can't she get her own solo movie instead of appearing in another Superman film?
There's an element of this in the new Spider-Man films, too, and for similar reasons: the "too many characters" complaint is getting slapped on the upcoming sequels in spite of the fact that for years now, fans have been open about their enthusiasm for eventually seeing a film where Spidey faces the Sinister Six.
"Is it So Hard to Just Do a Story From The Comics?"
For the sake of argument, we'll just ignore the legal situation at Marvel, where their characters (who exist in a shared universe and often interact in the comics) are split between different studios for the purposes of movies.
Comics have decades of built-up continuity and every minor character is somebody's favorite, which means there are (and have to be) a number of big stories where minor characters or arcane bits of mythology play a role.
Look to DC's '90s crossovers: they sold like gangbusters and the big fight-orgies might be cool to see onscreen, but would Final Night make a lick of sense without Emerald Twilight and Zero Hour coming first? And for that matter, could you realistically make a Zero Hour film?
Marvel's a bit better, since there's a revolving timeline that keeps the deep pockets of history from having too big an impact...but if you made a Civil War movie and Thor killed a fellow superhero instead of Clone Thor, fans would go ballistic at this mangling of the Thunder God's character. And on and on.
Everybody wants the movies to adapt their favorite stories, but when they do, all anyone can focus on is what wasn't exactly the way they pictured it, totally ignoring the fact that comics and film are different media, and that changes to accommodate the format will be necessary. Also, changes to suit the times. Yeah, Bishop wasn't in Days of Future Past in the comics...but he's a popular, time-traveling character who has been introduced since and his presence in the film makes total sense.
"The costumes and/or physical appearance of the actors isn't exactly what I expected."
This one ties into some of the others, but it's virtually impossible to take a costume from the comics and create a movie where non-comics fans can look at a poster and say "that looks awesome." People will point to Christopher Reeve's Superman: The Movie, but the movie industry was a very different place back then, and so are audiences. It's no longer difficult to believe a man can fly; audiences weren't even that impressed by Green Lantern fighting a giant cloud-monster in space with his enormous glowing ring-constructs.
The look of characters is another one, and it ranges from understandable to absolutely moronic. Being upset that Perry White or Johnny Storm isn't going to be white anymore doesn't make you inherently a racist, but it's probably misguided. Those aren't characters whose personality is tied in any meaningful way to their race, and the nature of film is that they aren't marketing exclusively to 25-year-old white guys like comics are generally guilty of doing. Other people will occasionally need to appear onscreen.
And the whole thing where an actor is cast and everyone immediately takes to Twitter to complain that s/he doesn't have the muscle mass or physical build to play the role is a step beyond that: it's just dumb. Anybody ever see The Machinist?
That was Christian Bale's awards-bait 2004 movie, and one of the (if not the) last thing he did before Batman Begins. According to the DVD commentary, he lost 62 pounds, reducing his body mass to 120 pounds. He later regained the mass, plus an additional sixty pounds through weightlifting and diet, for Batman.
Obviously Gal Gadot and Dane DeHaan didn't start with the "emaciated husk" look. Meanwhile the studios have the best and brightest physical trainers available in the Western world on retainer and ready to make that dude from The Tudors look like Superman.
"They changed [insert character or concept here]!"
This is one of the toughest ones, because the reality is that sometimes changes don't work. And when they don't, it's easy to look back at a film and go, "Who the hell thought turning Galactus into a giant cloud was a good idea?"
But then you get people throwing a fit because a character's race is changed, or Spider-Man's webshooters don't work the way you remember (it's not fair to pick on the "no organic shooters" people since the organic shooter-supporters got equally crabby about The Amazing Spider-Man going back to tradition).
Part of the reality of adapting a work to the screen is that there will have to be changes made to accommodate the medium and its needs. Comics are change-averse, having built up seventy-five years of history that audiences and creators are intimately keyed into. Real life is not change-averse, and sometimes that's frustrating for comic fans, especially when movies are made to appeal to the widest possible audiences by appealing to a "real-world" aesthetic.
There are times when things legitimately should not be changed...but more often than not, you don't know that before the first trailer ever rolls out.
Nevertheless, by the time we see our first glimpse of any given movie, many fans have already made up their mind because it's not the way they remember it from the comics.
Marvel Studios has made a number of really enjoyable movies in a fairly short period of time, but that doesn't make them infallible. Neither does it make Iron Man 2 or The Incredible Hulk a better film than The Amazing Spider-Man or The Wolverine. "Marvel" isn't magic, and this complaint is not only nonsensical but it makes you sound like an entitled fanboy.
Just stop it. If the rights are going to revert, they're going to revert (see Daredevil).