We're all well aware of the billion games Mario has been featured in. From huge successes like Super Mario Galaxy, to epic failures like Mario is Missing, there's a Mario game for everyone... except FPS Mario. I don't think that would fair too well. Although, Donkey Kong 64's mulitplayer mode had third person shooter, and the buffoonery of apes shooting each other with fruit guns was quite entertaining.
There's one Mario game in particular that stood out to me: Super Mario RPG. I'm not talking about the 2-D, side-scrolling Paper Mario series. Those were fine, but the one for Super Nintendo was special. Nintendo took a bold move, drastically shifting its gameplay and giving it the isometric view. They stayed true to the RPG formula. Mostly because they teamed up with Square (aka Square Enix).
I really liked how you team up with Bowser to fight a common enemy. There's so much ingenuity and authenticity in this game, it remains as a Super Nintendo classic to me. If they hadn't went the Paper Mario route, and expanded on what they already had, I think there could've been something truly amazing.