First Party was good on the Gamecube, but 3rd party exclusives probably gave it the magic dust, the likes of Resi 4, Viewtiful Joe, Star Wars series, Monkey Ball, Tales of Symphonia, Billy Hatcher, Geist, Twin Snakes, Skies of Arcadia
They might not all be massive sellers but they set the console apart and make it feel special.
If only a couple of third parties stick by the Wii U I do think the console will feel it.
In the past I've bought a lot of first Party content on my Nintendo consoles, but they don't always do it for me nowadays. You sometimes need that something else.