I never said that. I said that this one attack vector, which is rather easy to defend against, is so far only present in the PS3. Sony screwed up with their encryption implementation, in such a way that the private key used to digitally sign official software was able to be reverse engineered. This means that anyone can now create software that the PS3 thinks is legitimate, and the only way to fix this is to change the keys used, invalidating each and every single game sold for the PS3 to date. And no jailbreaking is necessary for a PS3 to be open to this attack, since with the private key, anyone can make software for the PS3 that is indistinguishable from a trusted, Sony-approved game.
No other company I know has screwed up this badly, or even just let their private key be leaked, and Microsoft is certainly not one of them. The XBox, Windows, Linux, the Wii, etc. and even the PS3 are attackable in a lot more ways, but they'll be trickier, and almost certainly involve jailbreaking.