Sony
Kind of self-explanatory. Even if the hardware wasn't over-priced it was certainly over-powered. Letting go of their massive casual user base was probably their greatest mistake.
Microsoft
Messed up big time on their hardware - Heavily unreliant. Lost a shit-load of potential by rushing Rare's games out of the gate and by underestimating the power of their IP's who all seemingly died (except for a few, who got their quality cut in half).
Nintendo
Letting go of the already few "hardcore" gamers. While it most certainly was a wise decision business-wise, people like me would have rather seen great graphics and third party support than a bunch of games where you shake your controllers to try to get back in shape.
Edit: It's funny because the poll currently looks like a penis.
