None of them are underrated
NES + SNES are praised for bringing gaming back
N64 has a core following that it deserves but I don't think it's underrated
GC gets a lot of hate minus a few fans but it deserves it
Wii has a mixed view and it honestly was a mixed console
They all deserve what they get IMO.
However, the thread is most underrated and isn't asking if any are. So the most underrated is the N64 just cause.