These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
No superhero crossover film had ever been done beforenote At least for American superheroes, and most of Marvel's biggest supers were in the hands of other studios. All they had were mostly B-listers. Even the Nick Fury stinger at the end of Iron Man was inserted mostly then as a Mythology Gag. Great idea in hindsight, though, right? In fact, because of the MCU (especially The Avengers), said B-listers were elevated to near-Spider-Man status.
This has also affected every film since the Avengers. A third Iron Man and sequels to both Thor and Captain America? And yet critical response was mainly positive. Then they really took a gamble with Guardians of the Galaxy, with characters obscure even to Marvel fans, and again it turned out everyone loved it. And now Ant-Man will be a dud apparently, mostly due to Edgar Wright leaving.
After complaints about the female/minority superheroes not getting their own films Stan Lee revealed at a fan expo that Black Panther was getting his movie right after Ant Man and Dr. Strange, as well as that apparently every superhero will get a film eventually. Captain Marvel starring Carol Danvers was also later announced.
After fans objected to heroic comics characters like Alexander Pierce and Sitwell being made HYDRA agents, Agents of S.H.I.E.L.D. revealed that some of the people working for HYDRA really were loyal S.H.I.E.L.D. agents, and were actually brainwashed.
Fans of The Mandarin were naturally pretty upset when Iron Man 3 revealed that he didn't actually exist. This was fixed by a One Shot which showed there is a real Mandarin, who is just as angry as the fans at how his name was used. Another part was the writing team realizing the initial reveal caused a plot hole regarding the Ten Rings group in the first Iron Man film.
A minor one but some feel that there's too much comedy in the films. It doesn't help that a big part of the appeal for the MCU amongst fans is that it's Lighter and Softer than many comics nowadays, so those who like the comedy get pretty defensive.
Some feminist and social justice advocating fans complain about how many heroes are a White Male Lead. This may be quieting down now that Black Panther and Captain Marvel's films have been confirmed.
Some feel that S.H.I.E.L.D. has too big of a role and steals the spotlight from the heroes, while others like the concept and are happy that S.H.I.E.L.D. is getting some focus.
Should Civil War be adapted into the Cinematic Universe? Fan opinion on the matter is split between people who felt the event was just badly executed due to having multiple writers with conflicting viewpoints and would love to see it salvaged on the big screen (pointing out that Marvel Ultimate Alliance 2 did do a good version of the plot), and others who think Civil War was always a bad idea and hope Marvel Studios avoid it. Complicating this is how an MCU adaptation would have to be drastically different from the original, which had the US government starting up a Superhuman Registration Act. Most obviously, there's the lack of any secret identities among the MCU's heroes, and any secrets they did have are public knowledge anyway after Winter Soldier. With the film now on its way, fans are hoping it works out.
The news that Iron Man will be in the third Captain America film, together with Chris Evans saying he wants to move on to other work, has a lot of people understandably worried about the MCU's biggest Spotlight-Stealing Squad getting all the attention in what may be Cap's final appearance.
The possibility of Spider-Man appearing in a future movie due to Sony either making a deal with/selling the rights back to Marvel Studios. Some people are ecstatic about the idea (and believe it would be better for the character than what Sony has been doing with the franchise), others think it could bring unnecessary baggage or reduce him to a Advertised Extra, and then others who are enjoying the latest films and don't want to see them get axed prematurely just because they get a lot of hate. Though the issues are a lot less about the character's presence in the MCU and is more about Marvel getting the rights back in full as opposed to a rights-sharing agreement.
The absence of a Hulk sequel in Phase Two and Three has also been a source of controversy. One side is upset that another solo movie with the not-so jolly green giant won't happen until after the fourth Avengers movie, especially after several statements from Feige and company that there was interest in making another movie after Age Of Ultron. Conversely, others are happy that Marvel's Phase Three lineup is focusing on lesser-known characters like Black Panther and Doctor Strange.
The rumor of Benedict Cumberbatch being cast as Doctor Strange. It really just comes down to whether you think he's a good choice for the role or not.
Creator Worship: Kevin Feige gets a lot of this from fans, some of whom have even argued that he's doing a better job with these characters than the comic writers themselves are. Though he's recently been taking heat from the reveal that the Wasp is a Posthumous Character in Ant-Man.
Joss Whedon as well, but that's par the course for Whedon.
Peggy Carter as played by Hayley Atwell got major acclaim from Captain America: The First Avenger, unlike the comics where her role is very minor. Despite the end of First Avenger preventing her and Cap from continuing their relationship, Carter returned in her own short film, cameos in The Winter Soldier, Agents of S.H.I.E.L.D., Age of Ultron, Ant-Man, and even got her own TV show, making her the first leading lady of the MCU.
Tony's Arc Reactor being a reverse-engineered Tesseract. Possibly confirmed as of Captain America, due to Howard Stark, one of the original inventors of the Arc Reactor, being shown recovering the Tesseract at the end of the film.
Loki letting himself be defeated at the end of The Avengersso he could be taken to Asgard and steal the Infinity Gauntlet for Thanos. Could possibly happen given how Thor: The Dark World ends with Loki seemingly usurping the throne from Odin.
Coulson returning in Avengers 2 resurrected as the Vision. Coulson was brought back from the dead via Project T.A.H.I.T.I. following Avengers but before Agents of S.H.I.E.L.D, but the Vision has since been confirmed to be JARVIS.
With Clint's absence during the bulk of Phase 2, a popular theory from non-Clintasha shippers is that he spent the time with Mockingbird, either having solo adventures or just relaxing and recovering. A slightly less-serious one is that he had to take time off following the Loki mind control thing and the subsequent breakdown he likely had, just as Selvig did (complete with naked Hawkeye).
A popular, half-joking theory is that Stan Lee's recurring cameos are actually the MCU version of Uatu the Watcher, taking a human form/avatar to observe the events of the films. That actually would explain a lot...
A lot of this from the DC side tends to cross into Sci-Fi Ghetto too. A lot of people have expressed the view that the MCU is for stupid children while The Dark Knight Saga and Man of Steel are 'dark realism', and as such are better/for smarter people. While this ignores that the MCU can be rather dark at times and has plenty of content that isn't really that kid-friendly (the fact there's asex scene in the first twenty minutes of the first film in the MCU seems to be ignored and forgotten), it also ignores that the DC films are also still rather popular with kids despite their perceived maturity, that DC have had a lot of films with a similar tone to Marvel's current films, or, you know, that there's a difference between tone and quality.
With Marvel movies not made by Marvel Studios, such as Sony's The Amazing Spider-Man Series and Fox's X-Men and Fantastic Four (2015) series. A lot of MCU fans wish these franchises would revert to Marvel, so such films made after Iron Man (not before), like The Amazing Spider-Man and X-Men: First Class are often dismissed as mere cash grabs made just to keep the rights from Marvel Studios. On the other hand, there are fans who believe that Marvel Studios simply doesn't care enough to buy the rights back (which is an option for them), since they make money off Sony and Fox's movies anyway and Marvel's in-house movies are performing spectacularly on their own.
A few fans seemed to favour Ashley Johnson's character (the blonde woman who appears several times during the Chitauri invasion) as a potential love interest for Captain America.
Some fans feel that Captain America had a lot more chemistry with Black Widow in Winter Soldier than he did with Sharon Carter (who shares one scene with him), and that it ultimately went to waste.
Hawkeye and Widow are pretty popular, but are as of yet not in a relationship as far as we can tell. Widow denies any feelings for him, and while the two are friends, they don't have any obvious romantic intentions.
Hilarious in Hindsight: The fan theory of "Hawkeye was absent for most of Phase 2 because he was having adventures with Mockingbird" is this thanks to Mockingbird being announced for Agents of S.H.I.E.L.D. season 2.
Internet Backdraft: There's been a theory springing up that Marvel are sabotaging the X-Men and Fantastic Four franchises in order to weaken Fox's success with their films; the evidence of this is based on their reduced presence in the comicsnote which isn't true; The X-Men are currently one of the biggest lines they're producing, with more spin-offs than ever; not to mention, the next big event is an X-Men/Avengers crossover event , Wolverine being killed off note which is no different than any other 'big shocking deaths', and is being used to launch several miniseries about it AND a new ongoing about Spider-Man and the X-Men, as well as attracting tons of publicity to the X-Men line as it is , Fantastic Four's comic being cancelled note which has been underselling for a while, and while not the worst seller, its still been pretty bad and doesn't have the cult following that their other books have , lack of merchandise produced for X-Men: Days of Future Pastnote which wasn't true; there wasn't any children's toys produced, which is largely down to licensing issues, but the film was not exactly a kid-friendly film and so wouldn't really be smart to make toys for; they still sold Hot Toys collectables for them though, are still selling toys for the franchise in general, and sold toys for the film before that, the lack of animated shows about either note ignoring that Wolverine did get an animated movie recently and has appeared in their other cartoons, but given the current quality of the recent cartoons, maybe not making the X-Men have to deal with one is a good thing , and a memo apparently sent out asking for artists to not send them Fantastic Four artwork note the actual validity of this memo is questionable at best . The theory itself, of course, makes little sense when you think about itnote how would cancelling Fantastic Four harm the film's gross? How would killing off Wolverine harm Fox's X-Men films? There's nothing stopping Fox from producing their own merchandise for the films , but it hasn't stopped people buying into it, including Rob Liefeld (of course, Liefeld's creations are tied with Fox's licenses, so of course he'd be on their side over this).
Iron Woobie: Pretty much every single one of the Avengers, to different extents. They all suffer a great deal, but have instead strove to move past their problems and fight for what's right regardless. The Guardians of the Galaxy, Team Coulson, and many of the other groups are this as well to different degrees.
Jerkass Woobie: Loki. He may be a homicidal, Axe Crazy megalomaniac, but it's very hard not to feel some sympathy for him, especially in Thor.
Agents of S.H.I.E.L.D. gives us Grant Ward; anti-social, brooding, emotionally closed off, and secretly part of HYDRA, but also the product of years of abuse at the hands of his family and his only real father figure The Clairvoyant himself, Garrett. Its no wonder he ends up as he is.
"Captain Dorito", about how Cap's shoulder-to-waist ratio matches a Dorito. Has since become an Ascended Meme after Robert Downey Jr calls Chris Evans "Dorito" several times at Comic-Con 2014.
Memetic Sex God: Both Tony Stark and Loki get this a lot from the fandom. For their part, Tony is a renowned bachelor who is this In-Universe too, while Loki is a shapeshifting Pretty Boy who is a literal God, and is known in the mythology he originates from to go after Anything That Moves. Recently, Bobbi Morse/Mockingbird has gotten this from the Agents of S.H.I.E.L.D. fandom too, at least going by Tumblr.
Only The Creator Does It Right: Disney's films made under Marvel Studios almost always receive better reception from fans and critics alike over Marvel movies made by other studios after the beginning of the MCU. The sole exceptions seem to be the critically-acclaimed X-Men: First Class and X-Men: Days of Future Past (particularly the latter), both of which were made by Fox - though even these are cause for a Broken Base among viewers.
Possession Sue: Both Widow and Darcy get this a bit; Darcy is pretty much shipped with everyone because she works well as a stand-in for the shipper, while Widow, as the only girl on the team, tends to have her uniqueness stripped away and used as a placeholder for some female fans to get together with the other Avengers...but mostly with Hawkeye. Sad, considering how well Widow was written in the films. That said, it is possibly due to how well Widow was written that the phenomenon isn't as prevalent as it might be.
His role in the MCU, combined with Matt Fraction's epic-length Invincible Iron Man run, rescued Iron Man from the horrendous Dork Age he had been in since Civil War. On a larger scale it lifted him from the B-list to being one of Marvel's flagship characters like Spider-Man or Captain America.
The same thing has happened for Maria Hill; originally hated in the comics for her jerkass behavior towards the heroes and actions during Civil War, the MCU version has redeemed the character by making her a likable and badass S.H.I.E.L.D. agent that treats the heroes with respect.
The Hulk had to escape this twice. After Ang Lee's Hulk underperformed and was criticized as boring and pretentious, Marvel's The Incredible Hulk sought to make him badass and popular again. It only somewhat softened public opinion of the Hulk, but then The Avengers completely redeemed him by recasting him with the acclaimed Mark Ruffalo and giving him new relationships with the other heroes, most notably Tony Stark.
The Scrappy: Jane Foster gets a lot of hate, especially in the second film where many people in the audience felt that the romance plot bogs down the mythos and negatively affects the quality of the film.
The Earth supporting cast of the Thor films in general. Especially when they're the bulk of the criticisms that Dark World received and other complaints being they're not as interesting or entertaining as the Asgard supporting characters.
All the corners of the slash shipping tend to argue quite a bit. Tony/Bruce, Tony/Steve, Tony/Loki, Tony/Coulson, Tony/Rhodey, Steve/Bucky, Steve/Sam, Steve/Clint, Clint/Coulson, Clint/Loki, Thor/Loki, etc. Any two of these that aren't compatible with one-another tend to argue a LOT. Then there's the inclusion of their respective lady friends...
Since even before she was cast and brought in, Mockingbird has been in one with Natasha over Clint. As Clint's most prominent relationship in the comics, Clintasha shippers who've read up on the comics knew Bobbi would come in between Clintasha, and so have made a frequent point to argue over her, while Bobbi/Clint shippers from the comics have responded in kind. With Bucky being present, it leads to a three-way shipping war between Hawkingbird, Clintasha, and Bucktasha.
And, of course, Agents of S.H.I.E.L.D. came and gave Mockingbird a lot of ship teasing with Lance Hunter, including making him the ex-husband she has unresolved issues with, instead of Clint. Now, Huntingbird has gained support, and detraction, because of this.
The announcement that Janet Van Dyne will have died sometime before the story hasn't gone over well with some fans. Time will tell if the actual film averts this though.
Generally averted by many cases of Adaptation Personality Change that many characters, specifically minor S.H.I.E.L.D. agents, go through in the MCU. Pierce, Sitwell, Koenig, Hunter, Mack, and many others are largely minor Nick Fury supporting characters, so for the most part the general audience has no idea they're even a case of this.
WTH, Costuming Department?: With the sole exception of his suit in the first film, Captain America's various costumes have drawn criticism from some areas of the internet, either for being too camp and colourful, or for the cowl looking odd (The Avengers), abandoning the traditional stars and stripes (Captain America: The Winter Soldier), or for just looking ugly (Age of Ultron). Obviously, many disagree though, but its a popular sentiment.
Hawkeye's suit in The Avengers drew criticism for being his original Ultimate Marvel uniform, and got criticism for not being like his classic Marvel outfit. The creators listened and in the second film he's gotten an awesome new outfit that's a mishmash of his various costumes from the comics, complete with Badass Longcoat.
Deathlok and Mockingbird also got criticism for their suits in Agents of S.H.I.E.L.D.. The problem with Deathlok was mainly that his cybernetics are internalized rather than on the outside like his mainstream counterpart, with the result that his armor looks cheap rather than intimidating. Mockingbird got complaints just for not initially looking like her comic self, though this was corrected by her second appearance (her hair is shown to be blonde like in the comics and her outfit is basically a more muted version of her normal costume).
Daredevil's costume got some weary comments though in his case it's justified; the black ninja-esque outfit is the one he starts out with before upgrading to his actual costume.
The Woobie: Captain America, Star Lord, Agent Coulson, and Winter Soldier.