First off i'll disclose that yes, when I was a kid I was obsessed with the TMNT and the Green Hornet. So this is a fan's perspective.
The green hornet used to be back to back with the Adam West's Batman. What fascinated me as a child about the Green Hornet that Batman failed to do was the fact that there were two guys, who weren't much of anything, creating a tricked out car which was concealed underground and comes up on the hit of a switch. When they wanted to use it they would enter their garage by sliding down a pole. Before I was introduced to Batman and the "Vigilante" concept I understood the Green Hornet as the unappreciated hero and righteous vigilante. They would "roll" in their Black Beauty beat up guys and resolve things easily. The Green Hornet was the first exposure I had to the concept of the "good vigilante". (Batman used to let the commissioner into his lair in the 60's show)
Now, for the movie : I loved it. The plot itself: To be clear, it is not the focus. It isn't insulting, to be quite honest it's well paced and definitely will not leave you insulted. Bottom line, you won't walk out of the movie thinking, "well it went from A to B."
The movie is charming. It has some of the best visuals I have seen in an action film. On that note, the 3D conversion is excellent. It's on par with Tron-bear with me as i explain this. It's extremely tasteful in the fact that NOT a single frame has been left unadjusted from depth. The cinematography is award-worthy. It alone makes the film vibrant and verdant(had to).
I've glanced at the gripes of most of the critics, and you can too for verification, but I found something odd: top critics such as Ebert's highlight that the film doesn't know what it wants to be and others say it's awful, violent and tired. I am not going to offer a rebuke of these opinions, but my perspective is this- it was a charming film with enough inventiveness and funny dialogue. It's got some bromance and all that, without being overlong. There weren't many, if any, jokes that fell flat or felt forced to the audience I was with. It is violent, but if critics are referencing a particular scene,then I along with the audience found it very ironic(it occurs in the climax so I won't spoil it). Ultimately, most acquaintances who attended the showing and people who were at screenings really enjoyed it.
Acting: Seth Rogen DOES NOT ruin the movie. I'm not much of a fan of his, but he's quite alright, in someways perfect. Jay Chou, even though he isn't fluent, is a charismatic actor and even manages to poke fun at himself in the movie on this issue. They left the fighting system(a combination of Wing-Chun and Jeet-Kune-Do of Bruce Lee's) intact; though it is over the top. Christoph Waltz is EXCELLENT. He seems to play another hans landa, he has some hilarious lines and sight gags in the film(including some with a cameo by James Franco). Cameron Diaz on the other hand doesn't have much of a role. The acting is fine, and in some cases very good.
I'd urge you to give it a chance in spite of the rating on rottentomatoes. I am not working for sony or anything, but I am writing as a fan, who is concerned the reviews are far too harsh and unfocused, to urge others to look at the positive reviews and at least check this movie out. I'd like to see another one.