[starquake]

Although the handhelds have been backwards compatible, only the Wii and the Wii U had backwards compatibility. The SNES, N64, Gamecube and Switch did not have backwards compatibility.

[drrotmos]

The SNES and the Gamecube did have the Super Game Boy and Game Boy Player respectively though, but I'd probably count that as sideward compatibility rather than backward compatibility.

[dmonitor]

I said "past couple decades" for a reason. The N64 is pushing 30