What is the best 3rd party port on a Nintendo system.

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Street Fighter Alpha II on SNES was pretty crazy as it was effectively a Gen 5 game ported to a Gen 4 console.

Starlink: Battle for Atlas on Switch incorporates Starfox into the story while beign technically rock solid as well.

Dragon Quest 11S basically rebuilds the entire game to Switch specs while even improving it in some ways like adding an orchestral sound track.