There's a lot to say about a videogame character who can stay relevant and popular for thirty years, but Mario has done so. Through 2D and 3D, Mario has been a staple in gaming not only with his main series, but also with his spin-offs.
Way back in 1985 when Super Mario Bros. released (though PAL regions had to wait an extra two years before they could play) there was a certain charm in how it played, how it felt to control. I wasn't even born when it released, but the classic game stayed within the family, and I had my first taste of Mario platforming with it.
Of course, this was nearly twenty years after release, and my only exposure to Mario from before then was Mario Kart: Double Dash on Gamecube.