Apparently you’ve never heard of the Game Boy games Super Mario Land 2
and Donkey Kong.
Some people see, or wanted to see, NSMB DS as the heir of 2d Mario after Super Mario World. Many people do not consider the Mario Land games in the vein of the main series (which they were including NSMB DS for whatever reason).
I always saw NSMB DS as the heir to the Mario Land games, not to the main series. A game developed for the handheld requires a very different experience than one for the console.
For a decade, people have told me in a whiny voice that “2d games belong on handhelds, 3d games belong on home consoles”. I like playing multiplayer around one TV. I like the large screen. When games like Final Fantasy 6 and all came to GBA, it just didn’t seem the same. I’d much rather play it on the big TV.
I’m currently playing Final Fantasy 1 now and, while I have it on GBA form too, I prefer it on the TV.
The real reason why people were saying 2d Mario games belong on handhelds is because everyone was trying to treat 2d games as “second rate games”. Screw that.
Anyway, the context of why I said sixteen years was because the emailer was saying consoles had all gone 3d. So I pointed out how it took forever for a new 2d Mario to come out for handhelds which were not “has to be 3d”. Hell, they even came out with new 2d Metroids and hardly anyone buys those.
The only possible conclusion is that Miyamoto and other Nintendo developers didn’t want to make 2d Mario. They certainly wouldn’t have made NSMB Wii if NSMB DS didn’t sell 20 million copies and the Wii was in trouble.