N64 and Gamecube were too late. Nintendo gave Sony way too much of a head start both times, first giving 3rd parties a chance to get really comfortable with the PS1 and then giving the PS2 free rein to rule the world.
Saturn was too early. That botched early launch killed it.
Wii U's problems aren't a matter of too late or too early. Given it was 6 years since the Wii launched and 1 year before the 8th gen launched, 2012 was the right time for the next Nintendo system. It's just that the Wii U was so ill-conceived on every level that the timing didn't matter.
The Vita seems to be a case of a system releasing too late. Smartphones were really starting to cut into the handheld business by that point. The same system at thee same price released 2 years earlier would have had less mobile competition stealing its thunder and could have garnered some momentum.
The Atari 7800 was released too late. It might have had a chance if it could have come out 2 years before the NES like originally intended or if it was released instead of the 5200 in 1982, but by 1986 it was too little, too late.







