If there was no Nintendo hardware.... there would be no Wii.
Which is different from the PS3/360.
Really it's the on hardware manufacturer out of the three i'd deem needed.
If sony didn't make the PS3 they'd be 360. 360 there'd be PS3... either way, the games that would of been on one would end up on the other.
Or if they both were gone, they'd likely show up on the Wii.
If Nintendo wasn't making hardware... The Wii line would of never been born... nor likely would Natal or the Sony wand.