Those examples you cite are when Nintendo simplified the depth of the game. If you notice, the mantra only pertains to a game's depth in its second clause.
The Mantra's first clause refers to how easy it is to control/understand/use the game's basic mechanics. It is in this field that Nintendo's advancedments ala touchscreen and Wiimote have contributed.
The Mantra's second clause refers to depth, how much advancement is available for players to play through into once they've learned how to basically play the game. Not much in a game like Kirby's Air Ride, but let's take a look at some games that have simplified interfaces while deepening gameplay at the same time shall we?
The New Tetris (N64): Very simple instructions: rotate and fit pieces to clear solid lines, D-pad and 3 action buttons (easy to learn), but the block-building added a whole new dimension to it (difficult to master)
Super Mario Bros. 3 (NES): simple goal: reach the end without dying. platformer with 2 buttons and a D-pad, (easy to learn) but with brilliant and challenging level design, platformer puzzles, great power-ups and CHOCK FULL OF SECRETS. (hard to master)
DDR (various): extremely simple concept, step on the arrows in time with the beat. (easy to learn) But, with faster songs, freezes, and complicated step patterns that must be executed in specific manners if you want to avoid tripping... (difficult to master) (don't be fooled,
this is a hardcore game at higher levels)
Diablo (PC): extremely easy interface: point and click to attack, and play tetris in your inventory (easy to learn). With randomized dungeons, lewt, sockets, and PvP, this game is definitely hardcore (hard to master)
Hmm... Tetris? Mario? DDR? Maybe even Diablo? These games show how a simple interface doesn't preclude deep gameplay, and when combined lead to great success. For a further discussion of this with specific attention to old platformers versus new ones, read this
Gamasutra article.
The thing about Kirby's Air Ride is that Nintendo, being stuck to the traditional controller, lost game depth when they tried for Miyamoto's "one-button" game. But now with a game like Wii Sports Boxing, Nintendo has basically revolutionized the interface to create a ZERO-BUTTON game that ANYONE can pick up, yet has a serious amount of depth, especially if you want to take it out of the fast 3 x 1 minute Player vs Player rounds of Wii Sports and build a hardcore Punch-Out out of the same exact gameplay.
Again, we see how the interface was key in allowing Nintendo to break the lower barriers of traditional control in using simpler interfaces, and still retain enough context and input stream (A developer used that term in E32006!) to create meaningful interactions and deep gameplay.
~Carmine M. Red
Kairon@aol.com