To borrow a line from Shakespear:
"If there be nothing new, but that which is
Hath been before, how are our brains beguiled..."
That's really the only thing you have to understand if you are considering watching this series.
Yes Gatchaman CROWDS touches on themes used in other anime like Death Note, East of Eden, etc. (Does power corrupt? can the un-empowered masses make a difference ...