Nintendo used to limit the amount of games that third party developers could release (Konami created the Ultra label to bypass this). This ensured quality, something Nintendo used to value.
Yeah, and it worked - the NES had basically no shovelware, and it wasn't possible for companies like Konami to just create labels like Ultra to bypass that restriction.
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"The courtroom is the garden of holy judgment. Those with lechery in their hearts should leave this sanctuary at once!" ~Franziska von Karma