I'm going to take a cop out answer and say all of them. I've had the pleasure of experiencing them all and each brought us something that now defines what gaming is.
The 80's brought us home video games in earnest with IPs that are still reiterated today.
The 90's ushered in polygons and expanded the scope of gaming to the world,
The 00's reinvented gaming by capturing new age markets and portability.
The 10's married the home and portable markets together and changed how we buy games.
Massimus - "Trump already has democrat support."