The Wii was sold out for that first year pretty much everywhere and that was mostly on the back of Wii Sports. The other games were largely inconsequential, Wii Sports was the "gotta have it" thing for 2006/2007. The "second wave" of Wii hits really didn't start until Mario Galaxy in November 2007 leading into the much bigger boom period of Wii Fit + Mario Kart Wii.
Things like Super Paper Mario and Metroid Prime 3 probably did dick all in selling Wii systems. They just were along for the wild ride.
Third parties are not supporting because of the game pad per se. If Wii U was closer to the XB1/PS4 in power with a 1 year head start, it probably would get more third party support. Because it's closer to the 360/PS3 though there's far less incentive to make games for it -- you already have 150 million owners of those consoles, so the Wii's 3.5 million owners by comparision isn't a big deal.
