If Nintendo were only showcasing games developed AND published by Nintendo, that might be the argument.
They’re not though, some of the games they’re showing they didn’t develop or publish.
Nintendo says emulation is transformative, that due to the recompiler, it’s a new work. Do they have permission from all the rightsholders for third party games to make a transformative work?
Do they even have the permissions from artists who might have licensed their work to Nintendo for X game, but not for the newly emulated ‘Y’
No, it’s more like being a Rock Band, having 2 wildly successful albums then going in a another direction with a completely new, different sound for the third album, then wondering why no one bought it.