Sega 32X and Sega CD were pretty bad. The Saturn's pricing was awful. It was even worse for it's time than the PS3 is for now. Spitting on 3rd parties with the Dreamcast didn't help either.
Nintendo sticking with cartridges and expecting 3rd parties to have no other options was unbelievably bad. Making the Gamecube default color purple and shaping it like a lunchbox wasn't exactly helping get rid of the "kiddie" image.
For Microsoft I would say their repeated attacks on the Japanese market seem like an unnecessary drain on their funds.
For Sony obviously $599 wasn't the best plan in the world, but I would say the real mistake and the one that led to the $599 is that the PS3 was simply released 1 year too early. Prices of the parts were still too high and they didn't really have the kind of first year games they wanted to have out. If they had waited just 1 more year things would have gone so much smoother.
