The problem with Illumination is that they are cheap.
It will be hard to tell which film a random Illumination background character is from.
For example, I can take a random Despicable Me background character and some people may mistake said character from being from The Lorax or The Secret Life of Pets.
They just copy-paste assets for their films.
So, even if Nintendo will just outsource the animation to Illumination, it will still probably look cheap.
And mind you, this is coming from someone who unironically likes Illumination's films.>>101605759
They are the most fitting for a 2D Mario movie.
Since the art-style of the Famicom artworks and the manuals can transition well to Ghibli/Ponoc-style.
Especially since the illustrator was a former animator from Ghibli who worked on Nausicaä.
Same for Zelda.
But if they wanna go 3D, then they should probably get Polygon Pictures with a similar style to the 3D games, and for Zelda, the same animation studio that did Kingsglaive: Final Fantasy XV (Image Engine or something...).
Illumination probably can make a 3D Mario movie work if they ramp up the budget and effort, plus they create mostly all new assets.
Fire Emblem and Metroid can be done well by either Khara or Production I.G., or Polygon Pictures if they do a realistic art-style for Metroid and an art-style similar to the FMVs for Fire Emblem: Awakening and Fates.
Star Fox should be by Production I.G. and a 2D/3D blend, or a Jim Henson Productions film with puppets similar to the Super Famicom artwork and with similar puppetry to The Dark Crystal.
Kirby should be in 3D and probably by Polygon Pictures or with all new assets and a much more gigantic budget from Illumination.