The Green Hornet certainly isn't a serious movie, but I wasn't asking it to be, especially not with Seth Rogen. The action scenes are good, same as the photography, the special effects and the car. The dialogs are slapstick and appropriate to the tone of the film, which fits Mr. Rogen perfectly (unsurprising since he is a writer/producer on the piece).
The bad guy gets silly by the end, even though he starts really serious (except for his gun). I guess he caught whatever infects Seth on a daily basis.
The take on the anti-hero is a mix between the goofball and the over eager. It's a good thing the whole flick is silly, or it might get weird. Let me reassure you, the silliness stays reasonable, because it's not repetitive and the actors do not let themselves become caricatures.
It's not a masterpiece by any stretch of the imagination, but if you're feeling like watching something funny with a lot of bang, you'll be entertained.