Because of the vast library of Mario spinoffs, as well as the universe being featured in Smash Bros., there are many, many opportunities to play as Mario and his friends in a wide variety of games. The amount of characters to choose from can vary, from a smaller selection in most Mario Party games, to the huge roster of Mario Super Sluggers, but staple characters like the Mario brothers themselves, Princesses Peach and Daisy, Yoshi and Toad can be selected in dozens of games.
These games pose a choice. Is there one Mario character that you call your favorite that you choose anytime you are given the choice? Are you so loyal to this beloved individual that you look past how they play in a specific game and go to war with them no matter what? Or do you view the characters as mercenaries, to take to battle when it suits you and then cast aside when they are no longer useful to you?
I have no loyalty. I play as Bowser in Mario Kart, because when I first started playing Mario Kart 64, I liked that I could bully people and relieve them of their balloons without even needing an item. But Bowser's slow and unwieldy nature makes me steer clear from him in Smash Bros. and Mario Tennis. In fact, I generally ignore the Mario characters in general in Smash Bros. In Mario Tennis, I roll with Birdo in the original, but in the Gamecube version I was unimpressed with her skills and went with the hated Bowser Jr. instead. The only game where I really go with my heart and pick my favorite character is Mario Party, where each character is exactly the same. There, I usually pick the lovable Toad if he is available.
My brother is on the other side of the coin. He always picks Luigi. Always. Luckily for him, Luigi is a pretty solid character in most games so it works out pretty well for him.
Are you like me or like my brother? Who do you use in different games and why? If you have one character, what is it about them that you like so much?