Sega Mega-CD, N64, Gamecube, Dreamcast, 3DO, Xbox Series X
The first 5 each had their moments with some great games that on release couldn't be played anywhere else, or to the same quality.
The last is simply an accomplished console that has no real weak spots in terms of hardware and what it is/delivers, just let down by not having the exciting software releases that drove prior generations (with the same affliction for the PS5, but contrary to the Series X it doesn't get *everything* else right.. namely its visual appearance lets it down. And of course contrary to the Series X it *is* a successful console, its lack of inspiring new unique/generational games having not retarded its performance as measurably as for the Series consoles).