In my opinion, the best way to describe this movie is to say it's what happens if you put Kick-Ass with Scott Pilgrim vs. The World. (Both fantastic movies by the way, and to be completely honest, both superior to this one.) It's a good mix, but not one that takes full advantage of what made each movie a stand-out, either.
As a superhero movie this was only just above average. Somehow I envisioned this to be so much more, especially with Michael Gondry's direction. I recently read a newspaper review that stated Gondry's spectacular imagination is what sets this movie off. In my opinion that's only half correct. True, when his vision is put into full use, it's great, and makes good use of the 3D. However these moments are few and far between in the movie. Personally I found they could have benefited so much more if they made it more like Scott Pilgrim vs. The World in terms of visual style. SPvtW was truly visionary in style and execution. It also had a great balance between humour and action, something I felt this movie lacked, and as a result, the pacing of the movie is off at times. I think it's safe to say that one would be better off going into this movie for laughs, and not for the action, as there is definitely less of the latter. Perhaps this was what they were aiming for, as The Green Hornet is not like other superheroes, but I constantly found myself expecting one thing and then getting another, and consequently found the story of the movie to be quite unbalanced and jumpy. The action scenes are good, but to me it's not what the movie is about, or what makes it. The humour is better employed in this way.
Christoph Waltz and Cameron Diaz, in my opinion, were ill-used. They could have done so much more with Waltz, who, fresh from an Oscar win, could have really brought a whole new level to the comedic villain role if given more to work with. Diaz's character I thought was an empty eggshell. She isn't the damsel in distress, but she isn't the kick-ass female character either. She was just the female character for Rogen's Britt Reid to keep going back to, a remedy for his problems, a point of reference in the movie for the male protagonists and never anything more. Sure, she didn't become his girlfriend in the end, but this declaration of independence is less a statement than a delay of the inevitable – we know, in one sequel or another, she will end up with him, because in the context of the story, she doesn't seem to have any other purpose.
This movie will probably not make a dent in the world of superhero movies or movies in general, but still, it is a fun way to suspend realism and pass an afternoon. Definitely give it a try if you like Seth Rogen and/or superhero movies, but don't go in expecting The Dark Knight.