Charisma, comedy class and the cheekiest of grins. Few may have thought of Robert Downey Jr as superhero material prior to May 2008 (Charlie Chaplin, yes; international ass-kicker, no), but within 15 minutes of the start of 'Iron Man' it was obvious that director Jon Favreau had the right man for the job. As billionaire industrialist Tony Stark - aka Iron Man - Downey got the mixture of hubris and humour just right, bringing to life a character that viewers could cheer for and laugh at and leaving them wanting more - more of his hi-tech wizardry, more of his international ass-kicking and more of his will-they-won't-they? relationship with personal assistant/nanny Pepper Potts (Paltrow).

The sequel picks up where the original left off, with Stark telling the world that he's the man behind the mask and becoming even more of a global phenomenon as a result. His personal stock rises, Stark Industries' stock rises and closest friends Pepper and Lieutenant-Colonel James 'Rhodey' Rhodes (Cheadle) watch with hands over eyes as Stark tries to be protector of humanity and superstar at the same time.

But the saying goes that a man who is loved by everyone has many enemies and Stark now faces even bigger battles than before. The US Army wants the Iron Man suit. Senator Stern (Garry Shandling) wants to put him on a leash. Corporate rival Justin Hammer (Rockwell) wants to be top of the heap and a Russian physicist (Rourke) wants revenge. And whether Stark will be alive to defeat any or all of them is in doubt: the very technology which is keeping him alive is also killing him.

Watch a clip from 'Iron Man 2'.

If it's crash, bang, wallop you want, you'll get your fill here. But while 'Iron Man 2' has more set pieces and brilliant effects than the original, it doesn't have as much charm - where that movie soared this one coughs and splutters a bit.

A lot of the joy of the first film was that the story stayed fairly small - we watched Stark as he built the Iron Man suit and then squared up to treacherous colleague and mentor Obadiah Stane (Jeff Bridges). 'Iron Man 2' has a bigger plot and moves faster; as a result there's a lot to be crammed in and less character development than you may have expected. And having assembled an all-star supporting cast, Favreau doesn't get the most out of them. Paltrow's Potts is there to tell Tony off and not much more. Johansson's mysterious Stark employee looks great in a catsuit and can throw a hell of a high kick but there's little else to the role. Rockwell is too one-dimensional as motormouth megalomaniac Hammer. Jackson appears all-too-briefly as spy boss Nick Fury, while Rourke had more to offer as the villain than the script allows him to.

They're the disappointments; saving the day once again is Downey Jr's performance. Recalling his own real-life experience as a bad boy who wised up, the coolness he brings to every scene leaves you thinking that you'd happily watch another four 'Iron Man' films once he was in all of them. The big challenges for future ones are how the character, his relationships and the tensions from the personal and professional can be developed. As the ending of this movie shows, there's only so much you can get from men in metal suits hitting each other over the head (especially after the original's finale), so Favreau, the scriptwriters or whoever takes over need to come up with better baddies and more tension. Sort that snag list out and 'Iron Man' can really do battle with 'The Dark Knight'.

Harry Guerin

Listen to the 'Framerate' review of 'Iron Man 2' from RTÉ Choice.