Actually, I have to give my vote to Wart, the final boss from Super Mario Bros. 2 (at least, that's how it was numbered in the States). Just something about an evil dino/lizard-thing who hates vegetables that appeals to me.
Can't decide! Can't de- /explodes/ I went with Peach, but my other favorites are Mario, Luigi, Daisy, Yoshi, and Toad IN THAT ORDER! Also, I secretly like Bowser. He's so funny to play as in Super Paper Mario! :3