Stellaris is a personal favorite, and it's great to see it make the leap to Xbox One, but Paradox and its partners could really seal the deal by bringing across mouse support, which the Xbox One now has. Hopefully we'll see it materialize down the line, but for now, the gamepad controls are pretty great as is.
The Hitman HD Enhanced Collection leaves a lot to be desired, despite supporting 4K resolution on Xbox One X and running at 60FPS. I'm not discounting each game's greatness for the time that they first launched — they were regarded as solid entries and still are — but as an HD collection they fall flat.
Despite the performance issues, Subnautica is definitely a title that you shouldn't sleep on. The open world exploration and survival mechanics are on point, and the world is massive, deep, and rich in detail; it's just a shame that it's being held back a little bit by problems with how it runs.