I almost put the GameCube for some of the reasons you mentioned. Also keep in mind that N64 sales were dead after Q1 2000. The remaining sales for the next 2 years were under 3.5 million. 

GameCube would've sold better with an earlier start, maybe even hitting 30 million or more. 

Majora's Mask and Perfect Dark could look and run better than on N64, even if they didn't take full advantage of the GameCube. I know it's a cutesy life sim, but all the GameCube ports of Animal Crossing had N64 graphics and few seemed to mind. 

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.

Yup, they should have moved Majora's Mask, Perfect Dark, Sin & Punishment, Conker's Bad Fur Day and Paper Mario probably should have been moved off the N64 and made for the GameCube instead. 

Fall 2001 launch for the GameCube was a disaster, especially since the hardware was finished by summer 2000. 

I think Gamecube honestly could've sold a pretty healthy 40 million units or so (more than the N64) if it didn't get caught coming out so late and then got into a pissing match with the XBox. 

While you're at it just ditch the dumb (but cute) mini-disc format, the GameCube actually was big enough as is to accomodate full sized discs anyway, they should have just released a seperate DVD remote accessory for DVD playback, that would have kept DVD royalty fees away from the base unit and if DVD viewing was what you wanted, you could just buy the remote (XBox did this, Nintendo was planning to do this with the Wii too but dropped it I guess because everyone had a DVD player by 2006). 

While it was still a massive success regardless, Wii could have released a year earlier as it was based on Gamecube hardware anyway and wouldn't have suffered for it, while getting an extra year on the market.

Exactly. GameCube software was starting to dry up a good deal by late 2005 (minus the crossgen Twilight Princess in Holiday 2006) and sales were effectively dead after Q1 2005. 

It's mind boggling that Nintendo made so many of the same mistakes with the N64 and GameCube. Namely the one I'm bringing up now where sales were dead 18 or so months before the successor even launched. 

While the Wii U was dead for a while, I get waiting until March 2017 to launch Switch. 2017 was a banger year for the Switch, after all. If Switch launched any earlier than November 2016, I feel like it would be super rushed. 

Yeah there are times when the hardware may be ready but the software isn't; the first several months of Wii U and 3DS for instance were very dry. 

Switch probably could've launched in 2016, but then it probably wouldn't have had the killer first year lineup it had historically.

Nintendo aside, it feels like Sega's timing was often less than ideal; Megadrive was well timed to take advantage of leapfrogging the NES, but the Saturn and Dreamcast both felt too early.

Amiga 1200 (and other Amigas with AGA chipset): much too late to stop the shift to PCs with VGA cards or even SVGA cards.