Xbox's backwards compatibility is much more complicated.
The Xbox One actually included hardware support for some Xbox 360 stuff like texture and audio formats.
However they recompiled the entire Xbox 360 software environment, OS, API's, Drivers, the lot and virtualized it.
They also repackaged the games, they take the PowerPC code, reverse engineered it into an intermediate, then emulate for x86.
Basically Microsoft did a hybrid approach. They have emulation, they have virtualization, they have partial hardware support, they recompiled and they used a translation layer to achieve backwards compatibility.
Nintendo isn't doing the same approach here, there isn't any need, they are relying on the fact that the hardware and software is an evolution rather than a clean slate.
--::{PC Gaming Master Race}::--
