Anyway, why should you watch it? Because it's more of an adventure story with lessons to learn for all ages. The story goes about this scrawny looking Viking kid, named Hiccup who just doesn't fit in with the rest of the strong, muscular Vikings. The main aim of the villagers are to fight and kill dragons which pillage their village of their livestocks. Hiccup couldn't even lift a sword let alone join the fight. Ironically, he's the son of the head of the village. Here, it's highlighted that fathers don't communicate with their sons.
Somehow, he catches the elusive dragon, Night Fury and couldn't kill the dragon. Instead he learns about dragons and their habits while trying to help the dragon he named "Toothless" to fly again. During the capture, Toothless' tail wing was injured, so Hiccup tries to help him fly again when he heard this phrase "A flightless dragon is a dead dragon".
In the end, it's nice how Hiccup reconciled with his father and the villagers learned to live with the dragons. The part where Hiccup rides Toothless (or the red dragon called Monstrous Nightmare) reminds me a little of Avatar where Sully rides the Toruk (which is red too). Lol
Sully riding the Toruk in the movie: Avatar
In short, I recommend you to watch it as it'll not be a waste of your money and time. :)
Other detailed reviews to check out.
In the meantime, I'll quote my friend, "I want a dragon!!" Lol