Does not deserve the praise
As a flash cartoon, you have mastered animation, and you have not cliched the action, which is a massive feat.
However, I feel that people are neglecting to point out that there was no explanation to the characters. This seemed to be the end of a saga, and the backhistories of the characters MUST be explained for this movie to deserve all the praise it is getting.
If we looked at this as a movie, and it was being compared to to a hundered other short films, you'd be lucky to get 70th place. I feel the connection between the centaur, the main character, the pixie, and the king need explaining. The graveyard warriors had no reason to be there.
My suggestion is make a prequel. Explain the people. Otherwise it's just so much violence backed by superb animation. But there needs to be plot.