I wouldn't say Nintendo is the only company who knows how to find "Blue Ocean" but they're the only company that is really looking for the "Blue Ocean". Guitar Hero, Katamari and DDR are games which appeal to people outside of the core gamer market that were not developed by Nintendo; the companies that developed these games tapped into a new market without looking for it by developing unique games.
The problem most companies face is that you're probably going to fail several times to create a new market before you actually create a new market. Nintnedo is the most successful with this because they always have multiple projects on the go which may or may not be successful. Doshin the Giant, Animal Crossing, Nintendogs, Electroplanktin, Brain Training, Odama, Wario Ware, and Pikmin are all unconventional Nintendo games that I can list off of the top of my head, if you look back at the history of Nintendo you'd find that in every generation they tried new concepts regardless of whether they would be successful.
I expect that one of the main reasons Nintendo has been reluctant to move towards the "HD Generation" is that it is not easy to make a lot of unconventional games if your development cost on the game breaks $10 Million.
