I have some of the original series, with Bruce Lee as Kato, but my memory's hazy. I certainly didn't recall details like who was the hornet himself, or what he did in real life, or other trade marks like the car. Mainly, I remember Bruce Lee being very cool.
So: Seth Rogen. Man child comedy actor guy. Not really action-hero material, you'd think, which is good, because the script doesn't require it. Yet again, he plays a self-absorbed git with daddy issues (daddy had a point, I thought). He gets into the hornet scenario because Jay Chou's Kato is a hero and can save people; Rogen just wants to beat up people (preferably bad guys) because "that was, like, AWESOME, dude!" Yes, by all means, let's make violence a goal in itself.
He then tries to turn his father's legacy - a once-great newspaper - into a vehicle for promoting his own character, while ignoring the fact that Kato's doing all the work. And if there's a second reason, it's to get into Cameron Diaz's pants. Deep.
All of this is supposed to be humerous, I'm sure. Possibly some of it is also the point (his self-promotion over Kato is explicit in the text, but the violence-is-fun message is not questioned). But it's not. It's really not funny. It's just dull.
Diaz walks through the film delivering her one-dimensional lines and putting in nothing else, because there's no space for it in the script. There's no chemistry between her and either of the male leads - but then, there's little reason to see why there would be: Chou's not the child Rogen is, but he only looks good by comparison.
Overall, I'm glad I've seen this, but I'm even more glad I saw it on a plane, and didn't choose to pay for it.