What a massive waste of potential. With the director of the masterful "Eternal Sunshine of the Spotless Mind" at the helm, the wonderful Christoph Waltz as the villain and the originality and classiness of Green Hornet lore, what could've gone wrong? Pretty much everything else, it turns out.
The first blunder, and it is a massive one, is casting Seth Rogen. For the first 90% of the movie, I absolutely despised his character - such a level of loathing for a main character not only makes everything else fall flat (I wanted him to fail), but it demonstrates just how stupid the idea of making Britt Reid an incompetent idiot, as opposed to a classy newspaper editor, was. Cameron Diaz is also terribly cast, not only for her terrible performance, but for how poorly she fits the role of the "super-hot but intelligent secretary" - the other characters drool over her, which just felt odd considering the age difference and the mediocre looks. Everyone else is just about average.
The biggie is, of course, the story. It feels like the scriptwriter was held at gunpoint and told to write something as quickly as he could. At no point is there any original element (save for what was already in the original premise), and the complete lack of motivation and the pointlessness of it all is only exacerbated by the terrible pacing and ridiculously long running time. Pretty much every cliché under the sun is here, smothered in a layer of plot holes, nonsense, contradictions and just plain bad writing.
Arguably one of the worst superhero scripts ever, and arguably one of the biggest wastes of potential ever seen in the superhero genre.