It's the rare Pixar film that doesn't live up to the standard of the brand. To my mind, only Cars qualifies as a so-so entry, not bad for a 15-plus-years run.
Dreamworks Animation, on the other hand, has a less stellar record. There's Shrek and its sequels (which have suffered from the law of diminishing returns) - and then there's mediocre work like Kung Fu Panda and downright duds like Madagascar and its sequel.
How to Train Your Dragon falls somewhere between the first Shrek and the third, in terms of quality (we'll reserve judgment on the fourth one until we see it). Like the least of the Dreamworks films, Dragon suffers from a shortage of jokes. But it has a strong enough story and animation to keep kids fascinated and even adults occupied.
Dragon is set in some distant fairytale past where Vikings all spoke with a Scottish brogue (apparently before they emigrated to Scandinavia). Or rather, all of the adults do; the kids all talk like American teens from California. But hey- it's a fairy tale (based on a series of kids' books by Cressida Cowell).
The story is told by a scrawny young Viking offspring named Hiccup (yeah, they all have cute names like that), voiced by Jay Baruchel at his most adenoidal. His burden - aside from being too small to fight the dragons that regularly attack the village and steal the food - is that he's the son of the village's brawny leader, Stoik (Gerard Butler).
Hiccup is dying to kill a dragon to make his bones, as it were. But when he accidentally brings down a rare Night Fury (a seemingly invisible beast that can't be seen because its black skin makes it invisible against the night sky) with his bolo-catapult and tracks the trussed-up creature to the woods, he finds he lacks the heart to slay the beast.