How To Train Your Dragon is quite simply Dreamworks Animation's greatest film (FULL DISCLOSURE: I was a character animator on this film and so, yeah, I might be a bit biased in this review). Why is it so obviously their best yet?
Because of the story.
In the past, Dreamworks has struggled with what many consider the most important part of any film--its heart. Readers of this site and those familiar with the Dramatica theory of story will know that the heart of every story is represented by a relationship. In previous films, DW often sacrifices this relationship for pop-culture references and irreverent comedy. Not so the case here.
In How To Train Your Dragon, Hiccup has not one, but three relationships that challenge his personal growth: his friendship with Toothless, his crush on the viking girl Astrid, and the classic father/son relationship with his headstrong father, Stoick. While there might be some hand-off of this all important Impact Character role between the first two (especially when Hiccup uses the classic You and I are both alike to describe why he couldn't kill Toothless), it really is the relationship with his dad that is at the heart of this story. Both don't see eye-to-eye and in traditional Steadfast Character fashion, Hiccup manages to break through Stoick's stoic attitude.
If you're a fan of Blake Snyder and his Save the Cat! series, you should recognize several key moments. There is the Fun and Games section where Hiccup and his fellow viking teens learn all they can about how to survive and triumph over deadly dragons (Note too that these are all the moments that ended up in the trailer--just like Blake predicted!). And then later you have the All is Lost moment where, if you missed it, Astrid reveals to Hiccup that he has "lost everything." You should also recognize the connection between the Opening Image and the Closing Image (Hiccup opening and closing his front door) and the transformation that has occurred. Blake's influence can clearly be felt in this film (his name even finds its way into the ending credits).
If there is one complaint about the story, it could be that there is too much heart. So much time is spent developing the relationship with Toothless, that there is little screen-time left to explain the Antagonist and the problem everyone is really dealing with. It happens so quickly and is painted with such a broad brush that there is little time to explore it with the kind of subtly and nuance that the relationship throughlines receive. When people complain about the big baddie being "convenient," this is what they are referring to.
But in the end, audiences want their hearts filled. What little of the Overall Story there is in this film, at least it is there. How To Train Your Dragon is a complete story and thus, lends itself to several repeat viewings...which I hope you will undertake with great enthusiasm (as do my wife and kids!).
It is my sincere hope that you enjoy this film as much as I did in helping to make it come to life.