In a tweet Microsoft's Aaron Greenberg confirmed that Crytek's Ryse: Son of Rome won't be rendered at native 1080p - instead it renders at a weird 900p.
"Update from team, Forza 5 is native @1080p, Ryse is native @900p, but Xbox One upscales all titles to 1080p & they look amazing"
We thought next-gen would be a place where everything was native at 1080p, but apparently that's not the case.