No real introduction, i'm just going to jump right in with addressing a few complaints about Marvel movies even though I know it will have zero impact on my fellow fanboys. So......
1. Marvel has too much humor.
Spider-man, the Thing, the Human Torch, Dead Pool, Ice Man, Iron Man, Star Lord, Rocket Raccoon, Hawkeye.... these characters are all funny in the comics. Read any story arc in Marvel and there is always humor. With Spider-man its constant. With Wolverine its the occasional gallos humor type of joke. It doesn't matter who the character is. Tony Stark is a snide prick but hes funny. Even Thor is unintentionally funny. My point is that if you have ever read any amount of Marvel comics you know that its loaded with humor. Im going to give you the heads up now and save you all the trouble of wasting you're time and money... Guardians of the Galaxy is GOING TO BE FUNNY. How do I know this? Because I have read the comics, to include Annihilation and Thanos Rising and all of those. Star Lord is funny. So is Rocket. Hell Drax, Gamora and Groot all crack the occasional joke. Quill jokes with Ronan, Adam Warlock and even Thanos. Personally I would have liked less humor in IM3. Not because it took away from the experience, I just didn't like that stupid kid.
2. Marvel movies don't have serious themes and content.
Hmmm.... A. Incredible Hulk, a young woman is about to be gang raped in a factory when Bruce steps in to save her.
B. Iron Man arrives to stop an ethnic cleansing as parents are being separated from their children and the attackers use them as human shields. One of those is a woman holding her baby and a man has a machine gun to her head. Yup, child's play.
C. In Thor a son plots to kill his brother and his father.
D. Bruce Banner describes being so low and giving up on life to the point that he committed suicide. He didn't attempt it, he did it. The fact that he didnt die because the Hulk is indestructible in no way changes that he put a gun in his mouth and pulled the damned trigger.
E. Nazis. When are Nazis anything but adult oriented?
That's 5 adult situations from 5 different Marvel movies. If you look into each movie a bit deeper and don't get fooled by the brite pretty colors and flashing lights you see there's much more going on under the surface of the movies and the characters. Because the colors aren't toned down and muted and the director isn't telling us that its supposed to be dark and brooding doesn't mean that there isn't much more going on with these stories.
3. Agents of Shield sucks.
Ya well, its much better then it was when it started, its EXACTLY what they told us it would be and they are tying the whole 1st season together nicely. The characters and plots are maturing nicely and the show is moving in a good direction. Simply sit back, be patient and trust that they have a much bigger plan for this show and these characters.
4. The Mandarin twist.
Seriously, the Mandarin is a weak ass character. The fact that they managed to get people to care in the 1st place was damned impressive. I don't care if they bring him back in some form. Just like I didn't care if Killian or Trevor was the Mandarin, I enjoyed the twist and will probably enjoy what ever comes next. What I cared about was getting a decent bad guy and a good story. I hated Extremis Pepper.
5. Character bastardization.
Ok, I give Marvel all kinds of leeway here because if they want to change a character in the comics to fit what they are doing in the movies... they can! More then that though... Marvel may change some things but the spirit of the character is usually dead on, and that's what matters. Compare Cyclops in the X-movies to his comic counter part. Is there any resemblance at all? I mean hell WOLVERINE IS TALLER THEN HE IS! That seems like a small thing but its not. Being short is part of Logan's character just like always having to look UP to Cyclops when they speak plays a role in their relationship dynamic. Point being the Cyclops that Fox gave us doesn't resemble him physically but more then that, he doesn't resemble him in the spirit of the character. Marvel may change somethings but the essence of the characters make them recognizable to the comic versions. That's really whats its all about. Giving us a version of these characters that does their comic counterparts justice.
Look at what Marvel is doing as a whole.. cinema, tv, Netflix, all one universe (I know that's not confirmed with Netflix but its a safe bet) all coexisting. If you're biggest complaint is "they are too funny" or "they aren't adult oriented" then you haven't read a lot of the source comics and you really aren't paying attention to the content of the movies.
As a side bar my favorite CBM's are the Dark Knight, Spider-man 2, the Avengers, Conan the Barbarian (with Arnold), Sin City and Iron Man 1. Man of Steel and Batman Begins are right there though.