They actually usually are bad, yet some are in the Great Valley. Do you think they are Bothtooth/Halftooth?
They appear evil in the first film, and probably would have eaten Cera had "the tar monster" not showed up. Also, they are not that nice in Journey to the Land of Mists either. However, they are in the song "Creepy Crawlies" with the residents of the Great Valley.
They are pretty sinister guys, but they aren't specifically labelled as Sharpteeth, despite having teeth, and, unless their previous includence was why Chomper was let in, one might surmise that they are omnivores.