Microsoft have confirmed that Crysis, Crysis 2 and Crysis 3 are now all Backwards Compatible on Xbox One.
Having personally played through all these when they first launched on Xbox 360 I can say that they are well worth checking for any FPS fan who has not played them already.
It also seems that the multiplayer servers for Crysis 2 are still up and running, the servers had thought to have been shuttered by EA but it seems the servers may have been transferred to Microsoft and they are currently still live.