I'm pretty sure Mario & Sonic is dead due to the IOC abandoning it to persue NFT iirc. Apart from that, I don't know. Maybe Baseball? To be honest, I never really cared for Mario Sports spin-offs.
For me it would be the Donkey Kong series. It just gets too old, and at this point, every new game just feels like it's copy of another one (the last few HAVE been). Now, don't get me wrong, Bananza is great, but all DKC games just feel the same...