While 400,000 is a strong start for the Wii U, the system's sales are a bit short of the Wii's first week numbers. In the same time period, Nintendo sold 475,000 of that system six years ago. (Read More: Will It Be 'Game Over' for Videogame Makers This Holiday? )
It's still selling, too. Nintendo says it sold 300,000 Wii system last week. Life to date, the Wii has sold more than 40 million units in the U.S. and is approaching the 100 million mark worldwide.
The 3DS handheld, which sold 250,000 units last week, continues to outpace the Nintendo DS, by about 1 million units, Fils-Aime said. Life to date, the company has sold 6.4 million 3DS devices.
Numbers aside, the Wii U's launch wasn't as smooth as some of the company's previous system debuts. A large, mandatory system update upset many users. There were sporadic system outages. And some anticipated features were not available at launch. (Read More: Nintendo Hits a Few Hurdles in Wii U Launch)
Fils-Aime downplayed the troubles, noting that, in some cases, they will result in a better service.
One instance of that, he said, is the delay of Nintendo TVii , which is aimed at improving discoverability for both over the air and online programming. Touted as a launch day feature, Nintendo delayed the functionality at the last minute, now saying it will release sometime in December.
"On launch day for us, Nintendo TVii wasn't at a point where we wanted it to be," he said. "It was not the compelling innovative product we wanted it to be and we needed it to be."
The Day One downtime of the system's online user hub, called the Miiverse, also caused some grumbling. Nintendo initially indicated it was an issue of over capacity, raising fears that when tens (if not hundreds) of thousands of new owners open up their Wii Us on Christmas morning, there could be more downtime for the system.
Fils-Aime said the Miiverse problems were not solely a matter of too many people trying to log on at once — though he declined to go into details about what other factors contributed to the problem. And come Christmas, he said, Nintendo is confident there won't be a repeat of the launch troubles.
"Without getting into a lot of technical details, the Miiverse [problem] was not purely driven by capacity," he said. "That gives us confidence that come Christmas morning, those servers will not be challenged in the same way. Come Christmas morning, the Wii U will be available globally. We know there will be a lot of consumers utilizing their Wii U for the very first time. So we're working very hard to make sure the initial customer experience is a good one."
Just as the Wii U's launch wasn't quite the clockwork experience many Nintendo fans are used to, the critical reception was a bit different as well.
Normally, new Nintendo systems receive effusive reviews, but critics were less admiring this time around. Most agreed that it was a leap forward for Nintendo, but took aim at the online experience and noted the Wii U was much less accessible than the Wii for people who were not core gamers.
Fils-Aime shrugged off the bad press, though.
"Reviews of a system or review of a game really come down to the quality and capability of the reviewer," he said. "There has been a range of comments and commentary. But when I go on Miiverse and see how consumers are reacting to games like 'ZombiU' or … 'Call of Duty', that tells me we're doing something very, very positive. Similarly, when I go on other consumer social networks and see other consumer reaction that is positive, I know we've done well."