I hadn't seen all of Eva before fairly recently, when I got the DVD boxset.... And I hadn't watched Kishin since I first got the LDs way long ago... But it really seems as if most of Eva's plot is straight out of Kishin.
You've got these aliens attacking for no apparent reason out of nowhere. They've got these cores that are very powerful energy devices. They tend to explode when subjected to severe trauma. There are subplots about betrayal and conspiracies to use the aliens for personal/political gain. There's subplot dealing with interpersonal relationships. There's kids fighting using big robots.
The only real difference is the timframe - Kishin during WWII and Eva after 2000.
So... yeah... sequel.