As far as I see it, Nintendo sees every 3rd party as competition on their console. All first party devs see this. But they allow them on because they know it's a necessity to their success. But I do think Nintendo is making more strides to allow 3rd parties a better competitive surface on their platform (by allowing Ubisoft to show off Red Steel as the first Wii game they ensured its success). And of course more recently they've taken on games such as The Conduit, Madworld, and Monster Hunter 3 to help 3rd parties see success on the console.
But in no way would they ever delay some of their or hold off on them for the sake of a 3rd party game. That's just a silly business model. Now they might delay, per se, a game releasing on the same week as The Conduit for competitive reasons but that's it.
But from their treatment of 3rd parties in the earlier days, Ninty has come a long way.
