The way I look at it is from a completely opposite angle, in the living room usability and
10ft interface (NO MOUSE or Tracker - I don't move a cursor on my TV)
Then I ask what could provide me with such usability - Can Kodi installed on top of Windows/Linux x86 box work - Sure it could, but would I need all that horsepower (and inevitably noise) just to play videos? Plus having full-blown general OS would also mean more manual maintenance sooner or later.
I always felt that just like separating audio processing and amplifying into separate boxes provides you with much better flexibility, the same goes for my living room media consumption.
In short, I rather have a small and simple media streamer device in the living room and a bigger server to be hidden away.
I used a bunch of various DIY solutions like various RasPi like boxes, commercial units, including a few FireTV and less known names. As long as I could Plex client running on it - it's generally good enough.
As far as gaming, I won't be the judge of it, as I strickly play PC games on my desktop PC setup, and I can't envision serious PC gaming with a mouse while sitting on the couch.
As for using a handheld controller, might as well just buy one of the new gaming consoles. God knows they are really packed with power nearly matching the high-end gaming pcs of today.