Played Super Mario Galaxy? Sure it was still the standard "Mario saving Peach from Bowser" plot but it still added more to the plot such as Roselina, the Luma, the whole idea of Bowser trying to create his own galaxy, etc.
While those may not be major changes to the overall series, it certainly adds something to the Mario storyline and to be honest I wouldn't want it any other way, but that might be just me.
As for a new Mario cartoon I'm kind of skeptical about this. It would be interesting but would probably end up mediocre at best. From what I've seen The Adventures of Super Mario Bros. 3 is probably the best adaption, though it severely lags in many areas. I do like the idea of a good adaption, but if Miyamoto really said that there will be no more adaptions then I support the decision.