The sequel has many shortcomings that are commonplace to every movie franchise. Iron Man is no exception to this. It tries hard to live up to the expectations set by the original. It introduces a load of prominent characters in minimalistic roles. Tony's frustration is captured well and so is Rockwell's rendition of Justin Hammer. As for the primary antagonist, Ivan Vanko aka Whiplash/Crimson Dynamo is not convincing and is one of the weakest villains any superhero movie has ever received. He is juvenile & his plans of exacting revenge are very immature & unplanned, to say the least.
Iron Man 2 (2010) comes in at #17 in my rank-ordered list of MCU Movies (#1 - Best, #18 - Worst).