Total Recommendations: 4
I'd be surprised if Blue Gender wasn't at least somewhat inspired by the Starship Troopers franchise. The similarities are immediately obvious. Both are Science Fiction stories about humanity fighting against giant bugs, both are very violent.
Jin-Rou also has war as central theme, a lot of disturbingly realistic violence, beautiful animation and will mostly likely depress the hell out of you by the time you reach the end of the movie. (don't watch Jin-Rou and Grave of the Fireflies in the same sitting, you'll go suicidal)
Monsters/aliens/ whatever disguised as humans eating other humans. Difference is, Kiseijuu is actually enjoyable.
both have the feeling of 'battle shonen with a added dash of desperation and carnage' and both are focused on a 'last' bastion of humanity fighting against a monstrous enemy. Differences are mainly in the setting, Sidonia is sci-fi in space with mechs, Shingeki is more grounded, fantasy oriented.