I would say:
1) Second screen tech (though, this is not exclusive to video games)
2) Smart downloads (start play before download is venue) almost never workds
3) Auto-update on Xbox One - I swear half the time its too stupid to move downloads to my external and just downloads nothing till I manually free up space
4) Picture in Picture on the Xbox One. When the console was new I was so fucking jazzed about the second bar to the right and watching games or keeping up with scores while watching TV, but it was killed quickly.
5) Console Streaming TV services. Sony made I think one TV show (Powers) and Xbox made a documentary. It was a dumb idea to do tons of original device-locked content... looking at you Apple+
Great examples and honestly some of the best of the thread imho.
What's interesting to me is, I think a lot of them will come back and be defining features of the next generation:
1)
Second screen tech sounds great but in reality, you want it built into your controller. And regrettably the Wii U was ahead of its time in this respect, I think. I feel this is a feature due a comeback, maybe not directly through controller input but through some enhanced engagement with your phone. XCloud will doubtless see some peripherals which help with this.
2)
Smart downloads this gen were subverted by devs who decided not to make them smart. Great example was GTA V - play within 20 minutes, all you see is a loading screen until the rest appears. Again I think next gen will redeem this as genuinely useful.
4) Honestly I was sold on
picture-in-picture when they revealed it. Picture in picture looked great until it, you know, didn't work. Stadia appears to be promising the same thing and I'm sure future streaming services will nail it; the use function in the era of streamers and synchronous multiplayer is far too useful for this to become defunct.
5)
Console streaming TV was another XBox One centrepiece and I still think there's a genre here waiting for its moment. Microsoft thought it was Quantum Break and a new Halo TV series. I think it's something more akin to Bandersnatch, and I sense we might see new hybrid genres next-gen.