The superficial similarity is there: invaders come to conquer earth and alien-in-human-guise fights them off, earning the admiration of unpleasant children. Beyond that two movies are not very much alike.
I can't be sure but I'm partly convinced that PRINCE OF SPACE was meant as a comedy. There's not a single person in the movie with even a shred of competence or dignity with the possible exception of the Prince himself, and even he makes some really dumb decisions. The aliens are devoid of menace, the scientists are helpless babies, and the children are selfish little snots good only at getting in the Prince's way. All these things stand in contrast to INVASION OF THE NEPTUNE MEN. The aliens are not goofy and, in the scene where they disguise themselves as human soldiers, they are even a bit menacing. The scientists put up strong resistance against the aliens even if, in the end, they need Space Chief to bail them out. The Chief isn't a swaggering buffoon--no "hahahaha your weapons are useless" nonsense from him--and his child fans get hardly any scenes.
It's almost like PRINCE OF SPACE is a parody of the story that INVASION OF THE NEPTUNE MEN plays straight. NEPTUNE MEN feels like it's trying to be a serious sci-fi movie...which is maybe why it's such a crashing bore compared to PRINCE OF SPACE.
I can't be sure but I'm partly convinced that PRINCE OF SPACE was meant as a comedy. There's not a single person in the movie with even a shred of competence or dignity with the possible exception of the Prince himself, and even he makes some really dumb decisions. The aliens are devoid of menace, the scientists are helpless babies, and the children are selfish little snots good only at getting in the Prince's way. All these things stand in contrast to INVASION OF THE NEPTUNE MEN. The aliens are not goofy and, in the scene where they disguise themselves as human soldiers, they are even a bit menacing. The scientists put up strong resistance against the aliens even if, in the end, they need Space Chief to bail them out. The Chief isn't a swaggering buffoon--no "hahahaha your weapons are useless" nonsense from him--and his child fans get hardly any scenes.
It's almost like PRINCE OF SPACE is a parody of the story that INVASION OF THE NEPTUNE MEN plays straight. NEPTUNE MEN feels like it's trying to be a serious sci-fi movie...which is maybe why it's such a crashing bore compared to PRINCE OF SPACE.