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