Nintendo needs to bring the next interface to the table.
The gap between you and the your virtual self is dewindling. As of now, controllers are needed. Still, those games that make the controller "transperant" and feel as if your in the game, are by far the most fun.
In SSB, an elite who wants to roll and dodge, doesn't think about pressing R and the direction....No...they just do it as if were a reflex (like walking is). If the controls aren't intuitive enough, then it takes far longer to reach that point (and ultimately, enough time to make most people lose interest). This is where Nintendo has to suceed. Making a controller that is very inuitive and that also allows for a degree of control not seen yet, is a key or essentially a bridge that makes gaming all mental.
When a game is all mental, your virtual self does exactly what you'd do in any given situation. Battling someone else who has reached that same level allows for a battle of wits to take place. Strategy is the basis of all games, so when your strategy succeeds it is very fulfilling.
I think Nintendo knows this, and it is the exact reason as to why they are down-playing graphics. Games like Contra, though very simple, were incredibly addictive. It was intuitive, and from the get go I was the person jumping, running, and shooting. I was put through hell where I attacked villians to save my own life, and because it was me who was playing, it felt very rewarding when I came out on top.
Nintendo's launch game is going to be intuitive heavy, but that doesn't mean it'll be simplistic. Contra wasn't simplistic in the time it was made. However, the same level of pick-up and play will be there.
Once they drop the controller bomb, I think we'll know exactly how games will incorperate both deep orginality and intuitive gameplay.