i tend to switch it up every time i play, but i love playing as peach, waluigi, daisy, and yoshi the most! though waluigi’s lanky ass legs have sometimes been my downfall , so i haven’t been playing as him as much lately.
it would be a travesty for me to play as anyone besides Waluigi lol, absolute god-tier tomfoolery there
you can bet I will fight tooth and nail to play as my favorite purple string bean boy, but if I had to choose someone else I'd have to go with Wario. he's actually my main in Mario Party 1 and 2 (because ofc Waluigi wasn't in those games) so I vibe with him immensely
I love Donkey Kong. I wish there were more playable characters. It's a crime that there isn't DLC for this game to add a more hefty roster. I loved Mario Party 5/6 where Koopa Kid was playable. He was my favorite by far. That game will always be one of my favorite games in the series due to the roster, but Mario Party 4 was a masterpiece. The boards were god tier.
I haven't played Mario Party Superstars (yet), but I have played all the ones on GameCube. I always pick the same character on GameCube and I know my answer would be just the same with Superstars: Yoshi!
He's my favorite Mario character and I always choose him in any Mario game; Tennis, Golf, Baseball, Mario Kart, Mario Party, etc. if Yoshi's an option, I'm picking him