I'm not really familiar with Jimmy Neutron, so there might be hiding a very popular franchise behind this film. Based on this film alone though, it's hard to imagine it did anything except for the youngest of audiences. It really feels like cheap CG-TV stretched out to a feature length production.
Jimmy is a smart kid, he just isn't very popular. That's about to change when parents around the world are being kidnapped by malicious aliens. Neutron is the only one who can save them, and with his band of outcast friends he sets out to save their parents from the extraterrestrials.
The CG is absolutely dreadful (well below what you'd expect the major US studios to put out), the comedy is terrible (it's just loud and obnoxious) and the plot is bland (but what did you expect). This really is for younger audiences only, though you may wonder if this is the kind of garbage you want kids to watch.