During the era of the PS3 and the Xbox 360, Microsoft had an edge on Sony by listing that all their games included a 1080p resolution, while most of PS3 games had listed their at 720p, save for a few exclusives. Of course, to the untrained eye it might seem that Xbox 360 was the more powerful console as it was believed to be capable of producing better graphics output. The reality of that isn't actually all that great. The reason why PS3 games listed their games at 720p while the same game on Xbox 360 was listed at 1080p, was simply because the PS3 game listed its native resolution, while the Xbox 360 game listed its upscaled resolution.
Now in the age of next-gen, the PlayStation 4 and Xbox One are the poster boys for better graphics and (hopefully) better native resolutions, though that doesn't seem to be the case either. Save for a few titles, most Xbox One games run at a native 720p, or up to 900p while PlayStation 4 games run at a native 1080p. How can you tell if a PS4 game supports 1080p? Just turn the case around. But what about Xbox One games?
It seems that Microsoft has opted not to showcase their resolutions anymore, most likely due to the increased focus on resolution by both media and consumers. Their games would now obviously be listed at 720p instead of 1080p (for ones that actually run on that resolution).
Just take a look here. Killzone Shadow Fall clearly shows that the game displays at 1080p, listed within the game's features.
Ryse: Son of Rome however doesn't have resolutions listed anywhere. And for that game specifically we know it's not running at full 1080p.
Could it be that Microsoft purposely left this information out? It wouldn't be surprising considering their competitor runs most of their games at full HD resolution. But why not just be upfront?