I think your doing a typical pointing out franchises that are very well known, but seem to fail to mention a lot of their recent stuff.
Luigi's Mansion 2 is still new, Splatoon is coming, Kid Icarus came back and even then they still make loads from it, Bayonetta is coming, Xenoblade Chronicles is coming, Devils Third is new, Fantasy Life for 3DS, Ace Attorney. It just buys me when people moan over it when there is loads. People just seem to fail to notice these days and it's sad.
The whole Mario and Zelda thing is like me saying well when will Ubisoft stop with Assassins Creed after doing over 7 games in just 1 generation or Call of Duty which you see pretty much all the time. What you think isn't much of a change is to me. I think Mario Galaxy was fantastic, even if you still had to save Peach, Zelda has been awesome, even with a Remake and A Link Between Worlds brought back the feel of a game that is around 20 years old and not done anything like that for a long time. Smash Bros is on 4th series as they do a game every 6 years, Mario Kart is always 1 game per generation and I call Gliding and Underwater and now Anti-Gravity a different and clearly people still like it and all I've mention is some of their best.
What your calling Mediocre is what people have bought in the millions.
Be surprised how many things you complain about, but there is still loads there that isn't always Mario or Zelda.