Mario Power Tennis. I can play doubles with Shy Guy and Fly Guy, and that's just the best thing ever.
Mario Kart is funky!
Mario Tennis is lovely!
Mario Strikers is kicking! (Lol pun intended.)
Some other Mario Sports game which isn't quite established as a series + compliment!
The Wario Platformers are teh awesomez!
The Yoshi Platformers are teh awesomez!
Well, there are two Mario Paint games, so I guess that counts.
The WarioWare series is groovy as heck.
You started mentioning other character games before Mario Party!?
The one you forgot. (Other)
Personally, I don't think games with "Yoshi/Wario" in the title count as Mario spin-offs.
*Poll option reserved for Meat Puppet*
... I hate Mario.
Mario Power Tennis. I can play doubles with Shy Guy and Fly Guy, and that's just the best thing ever.