I have to say, I was pretty disappointed with Avengers 2. The movie itself was well done and entertaining, along with the now classic Whedon quips. But the movie as a whole for me felt extremely retrogressive in terms of the storylines for all of the main Avengers.
For instance, Tony Stark. Discovering that an advanced AI resides inside Loki's scepter, leads Stark to attempt to merge it with the Ultron program he designed. He does this because true AI is beyond his current software capabilities, and apparently because of fears stoked in the aftermath of the New York alien attack. He fears that Earth may be unprepared for another such attack (Fury's same reasoning for making Tesseract weapons in Avengers 1). Stark, in Avengers 1 got on his high horse over Fury's attempts to use the Tesseract to protect mankind from aliens, something he himself does in Avengers 2 using the scepter. Of course, after the New York invasion and flying through a wormhole, perhaps anyone would change their mind, except...didn't Stark deal with those issues in Iron Man 3? His fear over the alien invasion essentially gave him anxiety disorder and led to him making over 30 additional Iron Man suits. A fear he leaves behind when he realizes his loved ones (Pepper) are able to protect themselves. A realization further symbolized by the destruction of all the aforementioned suits. Yet, in Avengers 2, all the growth from Iron Man 3 is essentially ignored as if it never happened, and we retread all that same ground. You could even argue, that Tony is essentially building weapons to keep people safe, the very thing he abandons in favor of pursuing his father's arc reactor technology throughout the course of Iron Man 1 and 2.
What of our resident god of thunder? In Darkworld, Thor gives up any claim to the Asgard crown and decides to be a "good man" rather than a great king. This prompts him to leave Asgard in favor of Earth and serve as Earth's protector. Now in Avengers 2, where does Thor's story arc go? He essentially leaves Earth for Asgard! Sure the reasoning is different, he sees a vision with the Infinity stones and suspects something greater is afoot. Essentially Thor's arc has less to do with him, and is used more a vehicle to introduce the audience to the wider world. The Aether, the Infinity Stones, etc. etc. In Darkworld Thor needed a reason to be on Earth so he is present for Avengers 2. In Avengers 2 he needs to leave so that he is not present for Civil War. I guess they could have come up with something better than just reversing what was just done.
Didn't I say not to do that Hulk? Hulk is in a very similar situation to Thor. At the beginning of Avengers 1 we find him in hiding and not really taking part in the wider world. Which, incidentally is exactly where he ends up at the end of Avengers 2. Sure, initially he was hiding from the military and now he is not, but as with the other characters the result is the same. Again, this is a plot device to explain Hulks absence during "Civil War", but a pretty weak one.
That brings us to the worst offender of them all, S.H.I.E.L.D. While Iron Man 3 was largely ignored by Whedon, so was Winter Soldier and the Agents of S.H.I.E.L.D. show Whedon helped create. Based on the events of Winter Soldier, S.H.I.E.L.D. is defunct as a government agency due to massive corruption via Hydra, and Nick Fury is believed dead by all but a few. Yet at the end of the film, he simply appears in a helicarrier with a whole crew of agents! None of those agents were on the TV show, where did they come from? How did Fury or Coulson or anybody in a now secret and independent organization get access to a massive piece of hardware like that? Doesn't Fury have a ton of questions to answer over his involvement with project insight? In essence, S.H.I.E.L.D. is exactly how it was before Winter Soldier took place, just like with all are main characters.
Think about it. If one were to watch Avengers 1 and then Avengers 2 without watching a single other phase 2 movie, would it feel like you missed anything? Iron Man 3's extremis soldiers and Tony's anxiety over New York, The Dark Elves and Thor swearing off Asgaard, to Winter Soldiers utter destruction of S.H.I.E.L.D. None of it mattered. The only thing that may come up is, "Hey, who's the guy with the wings?"
I think Joss Whedon is a good film maker, but an extremely poor steward of the MCU as a whole. If he's just going to ignore everything that happens in films he didn't make, then I have no reason to watch anything other than the Avengers movies. And that is bad for business. I will say that Captain America is an exception here, as in his vision we essentially see him let go of any illusion of "coming back from the war". All the people he new, and the world that was waiting after the war was over are lost to him forever, and he embraces being a soldier only. Pretty good stuff there.
Hopefully things go a bit better headed into Civil War. There is a lot of opportunity there, but I also have some trepidation. As Whedon had Tony Stark create Ultron, and he is without powers, and powered people saved the world from the blunder of a non-powered person, why do we need to register all people with powers again?