No, it's not important like the HD on the PS3/360, because the 3DS weren't meant to have the 3D effect as it´s main feature... so why the hell will that matter then? All the games released before with it enabled are all wrong aimed to the console, it wasn't made to display 3D images in the first place anyway [/sarcasm]
Comparing HD to 3D is nonsense.
3D is just a gimmick, it doesn't make much difference in gameplay or visuals,
it gives a better depth perception, and few games like SM3DL use it efficiently.
3D is so important, that Nintendo made 2DS without 3D.
Playing 480p games on a HDTV is just bad, it looks ugly as hell.
With TVs getting bigger and having more definition, it was a natural step to change from SD to HD.