The formula isn't perfect, first of all it's essentially only really valid for comparing 3d games. So if you compare NES or SNES games you have a fairly limited choice.
There's also an actual upper limit dependant on the viewers eyesight.
As for the Wii being at 0.5-1, thatseems too low. That is saying that making the Wii twice as powerful would make the games look almost twice as 'good' Clearly the N64 was at least a 0.25, gamecube 1 and Wii about 1.5







