Jon Favreau’s Iron Man (B+) is a giddy, inventive adventure that gives talented actor Robert Downey Jr. the role of a lifetime. As genius Tony Stark who refashions himself as a magnificent flying machine, Downey carries the high-flying comic book adventures on his shoulders. Quick with a quip and fast with the action, he grounds a new franchise with supporting help from Gwyneth Paltrow, Jeff Bridges and Terrence Howard.