I'd say either Zelda, or Mario.
The only reason I vote Zelda first is that most games are alike and are SO EPIC
And even though Mario can be epic too, the novelty of being a plumber in space fighting a turtle dragon is bit... abstract. And somewhat ruins the story in a few of them.
EDIT: But story isn't everything, and the game holds up amazingly in gameplay. It's great as well.
But Zelda keeps the legend going with each game, and especially with
TP and WW, I felt like a her as soon as the game started.
EDIT: I almost forgot. I've been so hyped on Zelda I forgot about my favorite game series of ALL TIME. Earthbound! It's amazing!