I think that the Siri Remote requirement at the tvOS launch killed any momentum for ATV gaming.
Before the launch of the ATV4, there were a bunch of rumors saying that the ATV4 would have been capable of Xbox 360 quality games. But the Siri remote requirement, and the 200MB limit to games may have scared away most developer support.
The Siri remote requirement has been remove since then, but it looks like it might be too little, too late.
I hope that the new ATV4K helps create interest for developers to bring some quality ports to the tvOS.
That said, there are a few good games and some good ports, but not many. The sonic ports are pretty good, and cheap.