(The verdict: Suicidal tendencies, none. There were no pinhead princesses or excruciating musical numbers. The only romance was minor, genuine, and subplot. I enjoyed it as a movie, not as something I had to watch with my kid.)
I loved the original How to Train Your Dragon. I am Swedish, so I am partially biased to Vikings to begin with. However, this was movie I saw before I had children and one I have watched for my own enjoyment without my daughter.
[How to Train Your Dragon 2](movie:44736) picks up with Hiccup, Toothless, Astrid, Stoick, and the rest of the original cast years later when Hiccup is 20. Stoick wants Hiccup to succeed him as chief, and Hiccup, of course, wants to explore and discover who he is. Enter the plot, which leads Hiccup to discover his mother who he (and everyone else) assumed dead.
At the heart of this storyline, like the original, is the relationship between Hiccup and Toothless. However, this story is more mature, a bit scarier, and a touch darker, all of which definitely speak to my cinematic preference. I will not leak any spoilers. I will only say that at least one scene of the movie brought this pregnant woman to tears.
How to Train Your Dragon 2, unlike many sequels (especially in the inflated and over-marketed children's genre), is not just a lazy regurgitation of the original designed to spawn a sea of merchandise. The two films are chronologically separated, and the sequel has an entirely fresh storyline that builds on the first rather than duplicating it.
I enjoyed the entire film--the story, the characters, the animation, the action--as much as I could with a 3 year-old climbing all over me while she spilled popcorn and candy over the floor and kept yelling at full volume. The movie definitely hooked my interest more than my daughter's, though with her, anything short of Frozen is no competition.
Ultimately, I might even prefer the sequel just slightly over the original, due to the edge and deeper development of the relationships established in the first film. Hiccup is no longer a child, so the movie overall is less cutesy. It is a safe bet that you might even enjoy yourself.