So far for the first nearly quarter of a century, it has to be online play.
Online play did exist in the 1990s, technically. But it was very primitive and limited compared to the last 15 plus years.
So much of gaming is dedicated to online play. Some games are online-only or online-focused. DLC is not online play in and of itself but is acquired online, and digital distribution has become the standard.
Honorable mentions: Motion controls (Wii, Kinect, PS Move, Switch, etc.)
Future paradigm shift possibilites in the next decade or sooner: SSDs (we're probably already there because of Series X/S, PS5, and PCs), VR (it's niche still).
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
