Probably Super Mario:
Super Mario Land,
Super Mario Land 2,
Super Mario Galaxy,
Super Mario Galaxy 2,
Super Mario 64,
Super Mario World,
Super Mario RPG,
Paper Mario: The Thousand Year Door,
Super Paper Mario,
Mario and Luigi: Partners in Time,
New Super Mario Brothers,
New Super Mario Brothers Wii,
Super Mario Sunshine.
I also used to own a copy of Super Mario All Stars on the SNES, but sold it long ago (though I bought it the Wii rerelease for one of my sisters as a birthday present, so I can still play it).
I'm pretty sure Zelda games come second as well. What can I say? Nintendo have great first-party games.