Well, actually two of the main selling points (not related to "sales age" but in terms of what Wii U should be able to offer) are:
Off-tv gameplay
Asymmetric multiplayer
THe first aspect is heavily marketed by New Mario (do you remember also the very first look they gave us of the Wii U at E3 2011?) while the second is heavily focused by NintendoLand.
Probably, while the remote had one major aspect to be presented (motion sensor = Wii Sport) Wii U has various different aspects (such as the two discussed, plus the Miiverse - once again presented by New Mario - plus the second window on the game universe - presented by Zombi - and so on) so we don't have just one game that becomes the icon of the console itself, but different games each and every one focused on some of the new features of the console
That said, probably none of those aspect is so strong as the motion sensor of Wiisport, but I have to admit that back in the days a lot of gamers were very suspicious about Wiisport if not worst, so the actual disinterest of gamers in those iconic games doesn't surprise me. Also back in the days thare was more interest in Galaxy (because it looked great, not because of wii-speficic elements), so I think that the disappointment we feel is because of the lack of a brand new game "for us". Gamepad or not.