There's always room for improvement.
Nintendo has an impressive, if not amazing, line-up of games this year, yet many on the sidelines came away thinking this was the worst Nintendo E3 showing in a decade. Mr. Iwata even made a semi-apology on Twitter for Nintendo's E3 showing in response to online criticism. That is a colossal marketing failure, one caused at least in part by too much preaching directly to the fanbase online and not enough outreach everyone else.
As much as Nintendo would love to manufacture buzz simply by telling the world how great their own games are, sometimes a less controlled approach is more effective. Nintendo Directs and Treehouse Live videos are great, but Nintendo needs to rediscover its E3 roots and put as many games into the hands of attendees as possible. (Who would have predicted the sleeper hit success of Scribblenauts at E3 2009?) Nintendo also needs to continually foster quality third party support, lest they continue to lose more of it to the competition. And as Microsoft has shown with Rare Replay, bold pricing can really turn heads, too. ('Sup, phantom Wii U price drop?)

Looking forward, if Nintendo wants to reclaim the high ground in the video game industry it needs to have an annual show of force. While the spectacle of the Nintendo E3 press conference may be missed in some circles, really what it takes to "win" E3 isn't a showy presentation, but the quantity, quality, and perceived value of the games on display.