It's hard to argue with success. This film made over $300M in theaters and even more on video, so there must be an audience for it. I would have assumed the audience to be in the single-digit age range, which was the age that I played with the toy, but I know a lot of my students went to see it.
There was a cartoon series with the same name, but I was too old to watch it when it was on, so I guess there's a nostalgia value for people who remember the series that ran in various incarnations between the mid 80s and 90s, similar to the Transformers. I was too old to play with the toys or watch the show when it was on. But for kids currently in their 20s there must be an appeal.
The movie had a decent script idea with a lot of funny pseudo-science, and a few funny references to the real world toy and shows. But this is not at all my style of movie. The huge amount of ADR in the film betrays script problems that appear to have been fixed with a lot of off-camera dialogue.
However, some nice casting raises the value of the film considerably, Randy Quaid, Marlon Wayons and Jonathan Pryce are good. Uncredited cameos are always a bonus as well. The movie did have a lot of nice sound design work in it, and I love Alan Silvestri's work. But I think I was just born too late to like this movie.