Iron Man 2
Avengers Contributions: Arc Reactor Renewable Energy Source / Introduction of Black Widow
As the first film released after Marvel Studios had firmly-established its blueprint for The Avengers, Iron Man 2 is arguably the first (and greatest) casualty of shared universe movie-making. In fact, it's a film whose shortcomings have only grown more apparent as better comic book movies - like The Avengers - have been released.
Iron Man 2's story is adequate (Tony Stark must unlock his father's research on a new energy source to save his own life), but the actual story beats of the screenplay missed the mark by a considerable margin. A lot of the problem can be found in what is now known as 'the Marvel movie formula': a rigid, three-act plot structure that spends three-quarters of the time telling a standalone character story, and one-quarter of the time shoehorning threads of the shared universe into the main narrative.
[caption id="attachment_60477" align="aligncenter" width="570" caption=""Sorry I ruined your movie, Mr. Stark.""][/caption]
Iron Man 1 & 2 director Jon Favreau has been pretty diplomatic about the whole affair, but in the years since Iron Man 2's release, we've learned how it was his friction with Marvel over creative design (including shoehorning those shared universe story elements into the film) that led him to depart the franchise and give up his desire to direct The Avengers. Even stars Mickey Rourke and Robert Downey Jr. have since come out and said that the sequel was a botched operation that never had a clear roadmap to follow.
Worse yet, the lack of commitment to any one direction (standalone story or world-building narrative) left the few elements of Iron Man 2 that were actually relevant to The Avengers - Black Widow, S.H.I.E.L.D.'s history and Howard Stark's new energy source - woefully underserved and/or overlooked. Silver lining (sarcasm): at least we got to see Tony Stark get drunk and goof off a lot.
This lackluster sequel clearly showed that Marvel Studios was still learning how to go about building its cinematic world effectively - and the fans certainly took notice. IM2 remains the weakest link in the Marvel movie chain.
Verdict: Iron Man 2 is a prime example (onscreen and off-screen) of how a shared movie universe gets built the wrong way.