To be fair, Microsoft is a better partner for Nintendo than Sony.
This is the key point: MS has better IPs.
Now, don't confuse it with MS using those IPs in a better way than Sony.
Sony actually explores their IPs and are active with them.
Microsoft does basically nothing with all the good shit it has.
Perfect Dark, Killer Instinct, Blinx, Banjo Kazooie, Conquer, PGR.
Even more recent, less successful cases like Crackdown show that MS has a lot of potential for IPs, IPs that are more suitable for Nintendo.
Sony only shits out try hard, adult stuff like Uncharted, The Last of Us, Killzone, Horizon and the sorts.
Sony Is are very diversify. They often fall on the same tone of games.
The last time Sony tried to so something different was with Knack and we all know what the led to.
With MS acquiring new studios like Obsidian and Ninja Theory, the IP potential is much higher.
MS has superior and more diversify IPs. They just don't know what to do with them.
Kinda like Sega