My problem with The Avengers is that Thor was too good. Specifically, Tom Hiddleston in Thor, whose performance I think matches the range and intensity of Heath Ledger's Joker. As Film Crit Hulk (my own film crit hero) points out, in The Avengers Loki serves to accentuate and develop the arcs of the six main characters. But this leaves less room to explore his own background and motivations.
Let's look at those anyway. From Thor, Hiddleston brings a feeling of resentment and ambition, but he also takes on something of the Red Skull's ideology in Captain America. Humans have weak minds imprisoned in frail bodies, and require a Nietzschean strong man to rule them. Happiness for most lies in the predictability of slavery — the alienation of the responsibility associated with free will.
And the way humanity decides to fight this evil is... to get a bunch of strong men to defend or avenge them. There is a tension here, which was brought out for me in a scene between Captain America and two cops, where the latter claim the responsibility of defending the innocent, before willingly divesting themselves of that responsibility as soon as Cap demonstrates his superior strength. This moment is played for laughs, and sure Cap's authority comes from charisma rather than fear — the fact that the Avengers use their power to defend freedom makes them the heroes. And the totemic idea of Phil as the rallying force behind the team gives an 'of the people' spin on their activities. I'm aware of all that. But when I remember Nietzsche's point that charisma is ultimately produced by fear, the vox pop platitudes at the end of the film leave me with some rather uncomfortable feelings.
Whedon's work always pits the small guys against the big evil. Without the army, Loki is just one big guy against six (which includes the Hulk). A more satisfying villain for Whedon would have been the shadowy (quite literally) cabal behind S.H.I.E.L.D, and the film takes some steps in that direction. Whedon undercuts Fury's endorsement of nuclear weapons; the problem of the alien invasion is solved without them. Retaliation is delivered in spite of what the Avengers were doing on the ground in Manhattan, and it is clear that it will have serious repercussions in the next film, as the strike draws the eye of Thanos. If Whedon is indeed to direct the sequel, I expect extraterrestrials will not be the only antagonists the new team will have to face.
ETA: There has been a bit of discussion about the relative objectification of Black Widow compared with Catwoman in The Dark Knight Rises. It did strike me when watching the latter that the Nolans were overtly taking care to ensure that Anne Hathaway was never sexualised by the film itself, only by characters in the film. On the other hand, The Avengers features a two-shot of Scarlett Johansson with Tom Hiddleston in which this happens (thank you internet). The thing to emphasise about the frame is that it does work on a character level — Black Widow as this rooted immovable object on which Loki is weaving his manipulative spells. But it also features a leather-clad arse squarely in the audience's face (i.e. a sexual object on which the audience are invited to...) POINT BEING, both of these things are going on. I guess for those not interested in Johansson's arse, the character stuff may be enough of a justification for the shot to be framed in this way, but I have to admit that it took me right out of the film. Points lost there, Mr. Whedon. Also, me.
Should say that I think in other respects Black Widow's character bests Catwoman's in the feminism game, in that the Nolans end up throwing Kyle at Batman as a consolation prize for his trials, while Romanoff is more self-defined throughout. It's tricky though, because both characters essentially conform to the same femme fatale archetype. I do like Whedon's decision to emphasize the way Black Widow consciously creates the impression of vulnerability in order to work loose the prizes she is after (an aaaage is spent establishing this trait at the beginning of the film). Using femininity as a way to exploit patriarchy for your own ends. It's not a new idea (you could argue the femme fatale archetype is built on this), but a good way of addressing her sexualisation in the future. Black Widow CHOOSES to be objectified. The impression of weakness is a weapon wielded from a place of strength.