Play all the games you can from the 80's. "Computers" like the Commodore C64 and Amiga, ZX Spectrum, Atari ST and others had games where the concepts of today's games were created. Almost everything we play today was "invented" back there.
The "trick" is to rediscover the concepts, ignore all the artwork and think on a twist or two to make that concept new again - think on Castle Wolfenstein ( https://en.wikipedia.org/wiki/Castle_Wolfenstein ), how it influenced so many games and how, even today's releases have that concept in their genes. It's almost the same thing with new technology and other enemies (police, military, terrorists, zombies, whatever you can think of).
We live in a time where "new" is just a remix of "old" - we call it reengineering :-D
Does this makes any sense to you?