Honestly, I'd say we do OP a favor and start categorizing everything.
We separate PS1 sales, cause the original model wasn't compatible with the special LCD screen you could get for the PSOne. So it's obviously not the same console.
We separate PS2 sales cause of the harddisk issue.
Only some PS3's were backwards compatible so we'll have to separate those as well, since not all PS3's can play the same games.
Later Wii's lacked the bwc mode with GameCube, so down it goes.
Nintendo DS didn't have an eShop like the DSi, so separate console it is!
n3DS had games that couldn't be played on the regular 3DS, so again, separating!
I'm sure Xbox One has some Kinect-only games so we'll have to separate launch models with included Kinect from the rest, since Kinect was pretty much unavailable during the rest of the gen.