Iron Man was an unexpected surprise of a movie. It managed to find surprising depth, suprising warmth and humour and it had inevitable scenes of blowing stuff up. And it blew things up really well.
Iron Man 2 has a lot of pressure weighing on it. Not only is it a sequel to an exceptionally popular movie but it also acts as a big link in the chain of the upcoming connected Marvel Universe of films. If it isn't very good then it bodes badly for the films to follow.
I'm pleased to say that it is a good movie, though unfortuantely it isn't a great movie. One of the most important aspects of a "big" movie like this one is the action and this film has it in spades, and each sequence is enjoyable, frenetic and has a very good pace to it.
One of the main parts where the film fall down relative to the first is in characterisation. The acting is as strong as the first film (with the merciful removal of the pitifully weak Terrence Howard), but the chances for them to shine are greatly reduced by an expanding roster of characters. Robert Downey steals the show again after a bit of a weak first 5 minutes on screen. Unfortunately the excellent Sam Rockwell is massively underutilised and his character doesn't really undergo any kind of journey, and is largely a foil for the plot. The same can be said for the character of Pepper Potts, Nick Fury, Whiplash, Black Widow... Which is a terrible shame. You could remove Scarlett Johanssen's character and it wouldn't have made any real impact on the movie. I'm sure she will be used elsewhere but I have no idea why she's in THIS movie.
Because of the increased cast there is a lot of "laying pipe" going on with the plot being layed out without really feeling like the character is driving it but rather that the plot is driving them. The worst example of this is the plot involving Tony's relationship with his father. Conveniently Fury knows more about his father than Tony does and we discover that Tony's father helped establish SHIELD. This seems extremely unlikely, and chronically convenient. Tony's estrangement issues go almost as quickly as they arrive as within minutes he watches a film of his father who leaves a message for him telling him how important his son is. This is coupled with a very weak stretch in that Howard Stark left a secret message for a new element in the layout of the 70's Stark expo model... It's a bit of a hideous plot contrivance, especially as this just so happens to be the solution to Tony's medical condition. WHAT ARE THE ODDS?
There are a few moments like this unfortunately, especially in the climax where the army of Iron Men are brought down within seconds after Tony's been running from them for 5 minutes. Added to this, the final showdown with Whiplash is embarrassingly brief and basically is the "don't cross the streams" gag from Ghostbusters. The strongest aspect is the relationship between Rhodes and Stark which is very strong and well acted.
In the first movie Tony was cocky, realised he WAS the problem, and then changed his ways to make amends. In the second Tony was cocky, realises he WAS the problem, blows lots of things up, but ultimately makes no impact on the central problem of proliferation and is then given a medal. Pardoned possibly, or at least forgiven, but honoured? He brought down Whiplash, but he's proven to be wrong in his estimations and it's proven that his advances are causing problems, so a medal feels very wrong here.
Despite these aspects of the film being lacking it is still an exceptionally enjoyable movie. The trademark humour is there, the charisma of the actors is there, it's just a shame that the story and writing is a tad on the weak side. It has flashes of great potential, with Tony's self destructive tendencies in how he deals with his life-threatening condition hinting for a time that this would be the dark middle film, the Empire of the Iron Man movies, but it all gets neatly wrapped up. It shows that Marvel can make good movies but so far they've only made one GREAT movie - the first Iron Man.