Kids like the humor, but lacks the depth of the TV series
Like other parents here, I regularly watch the Ninjago TV series with my children, so was looking forward to the movie. My daughters aged 7 and 8 enjoyed the movie quite a bit (especially the giant cat and some of the jokes), but the characters here were not nearly as well-developed as those in the TV series, apparently in an effort to make the appeal of the Ninjago brand more general. Unfortunately they lost a lot of the complex depth in the character relationships in the show. I don't know that my daughters missed it, but I sure did.
I'd been hoping for better, since brothers Dan Hageman and Kevin Hageman get story credit on the movie (they're responsible for writing the TV series -- on their own, no less; the film has six screenplay credits and seven story credits). The movie does no harm, but the emotional ambition of the series was missing. And no disrespect to Jackie Chan, he's no Paul Dobson, who's a much better Master Wu.