Third parties will never outsell Nintendo titles but that's not what third parties should aim for. They should aim for "enough". What I mean by that is don't expect your port to outsell Mario or Zelda and be happy if it breaks millions. It's harder to compete with nintendos titles because of the quantity and quality of them released yearly compared to Microsoft and Sony. Those two release what? 3-4 AAA exclusives a year compared to Nintendo? That doesn't mean there isn't room for third parties.
I'm a Nintendo gamer and I buy third party games when I know it's as fully featured as the other ports (not missing modes, DLC, poor performance, etc). If mass effect, Witcher, fallout, etc came to the NX there's nothing I'd love more than to have all those games on the same ecosystem with achievements and such. I wouldn't mind it if it was the worst performing version, at least I get the game. I would take the Witcher 3 or Fallout 4 at 900p30 instead of not having it at all.