Considering that when I see Yoshi plushies in stores, I have to go pick them up, cuddle them, say "SO HAPPY!!!", and scream over them for 5 minutes before I can continue doing what I'm doing, I'd say it's Link.
But no really, it's Yoshi. So FREAKIN' happy!!
Link and Lucas are close behind though. Link I think needs no explanation and Lucas...I mean, you go through as much heartbreak as he goes through and you sympathize with him so much throughout Mother 3. If you've played it, you know what I mean and if not, you need to get on that and play it.