I think people get too caught up on the metaphors and miss the big picture about what the "Disruptive" strategy is all about ... "Disruption" could best be discribed as a methodology for creating a new submarket which you control due to the lack of competition.
In the videogame market there is a small segment of the population who has been heavily targeted for several decades and the potential total revenue growth from this demographic is very limited because the majority of them are already gamers, and they are spending as much time and money on videogames as can realistically be expected. Because there is such high competition the costs associated with developing and marketing a product to be successful to these consumers has skyrocketed, and the margins from the sale of products to these gamers has shrunk dramatically, and the only way for a company to be successful is to "Fight" with other companies over their sales which results in a lot of "Blood in the water" and "Dead" competitors.
There is also a second (much larger) segment of the gaming market who may (or may not) enjoy some of the markets that represent the main focus of the industry at the moment, but they're not entirely dedicated to it and they have time and money to devote to games in genres which are not being focused on (or even produced at all) by the major players in the industry.
Finally, there is a (once again much larger) segment of the (potential) gaming market who is being very poorly served by the current market and there is almost no interest in producing products for them. (the "Blue Ocean")
A disruptive strategy is when a company focuses on the broader market (the middle group in the discussion above) while starting to find ways to appeal to people who are not being well served by the market at all (the "Blue Ocean"). You can see this in Nintendo's strategy because most of their conventional games are focused on genres where games sell well but have little competition (platformers, adventure games, kart racers, puzzle games, arcade games, etc) while they are producing games which are very unconventional, and there are few existing games which can be directly be compared to them (Wii Fit, Wii Music, etc).
The next step for Nintendo in this strategy is to use the techniques that have been applied in the dedicated and broader markets to convert new and underserved gamers into more dedicated gamers, and to solidify their dominance within the market. You can imagine what Nintendo wants to do with the market they have grabbed is what EA did with the Sports game market in the 1990s; which is to become the highest quality and best known product in order to ensure that people see you as the only product to buy.
Why it is so difficult to unseat the disrupter is because they have already improved the "Quality" of their product (in the eyes of their consumers), built their brand, and made their consumer more brand conscience by the time you release your competitive product. It would be (a lot) like releasing a crime based sandbox game today and expecting to be able to compete directly with Grand Theft Auto.