The last decade of the 20th century saw gaming transition from being primarily 2D to primarily 3D, a gargantuan paradigm shift that opened up a whole new world of possibilities.

Now that we're almost a quarter of the way through the 21st century, what do you think has been the biggest such shift for gaming since the turn of the millennium? 

It can be a new technology, a new feature, a new way of playing, anything like that. It can also be something that technically existed prior to this century, but didn't take off until this one, similar to how there were 3D games prior to the 90s, but they didn't take over right away.

What's your pick for the biggest step forward, and what makes your choice worthy of the top spot in your opinion?

Maybe motion controls? Though little bit gimmicky during Wii/360/PS3, it really was a big step forward for gaming. Gyro control in games such as Splatoon, the immersive use of such tech in VR, the catalogue of really fun games to come out of it like Wii Sports. Even made gaming a bit more mainstream.

Second generation MMOs shaped the gaming industry and landscape

I'd say online playing is the single biggest feature of this century. Just think on how many of the most played games would not exist without online playing, or would be significantly less popular without online playing

For me, it has to be online connectivity in the console space. I know Dreamcast made online support a priority before 2000, but it really found its footing thanks to Xbox Live in 2002.

And in the years since, it has completely changed how people distribute and consume games, and how they interact with them socially.

Online everything, from DLC and microtransactions to post-launch updates, online multiplayer and online features in non-multiplayers games. Especially combined with rising development costs, this has been a huge thing.

The century is still young, it will be VR/AR by the end of the century. VR is only at the point where early 3D was, when 2D games were still much better.

For the first decade it's definitely online gaming. It was there in the 90s, yet matured in the naughties.

Last decade I would say digital/indy games. Also already there in the naughties, yet last decade digital indie games broke through everywhere.

This decade, dunno. VR tech isn't ready yet for the main stream, nor is ray tracing to universally take over from baked lighting. Maybe this decade will be remembered for device agnostic gaming, cross platform, continue anywhere. But that's also not quite there yet. 6 years left anyway.

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).

SSDs, easily.
Now that good SSDs are being pushed by consoles and getting properly used by games, it's by far the biggest step up we have currently in gaming from last century.

I would have to go with VR as well. It's still in its infancy like 3D in 1995 and Motion control with the Wii. Even Skyward Sword was still a bit wonky.

Just look at Those new what, what are they,Google glasses or is it Apple glasses? Already took VR to new levels. Another decade and they will have it down.

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