At that point, gaming itself was relatively new. There weren't really any long-established franchises back in those days so people would try out anything that looked good. I'm not so sure that's the case anymore. Nintendo may have had a hit with the Wii series, but that's because of the Miis, which are basically putting yourself into a videogame, a concept that has mass appeal. Nintendogs and Brain Age also hit it big. However, many of Nintendo's other recent IPs haven't had as much success as their previously created ones, such as Pikmin, Sin and Punishment, Geist, Chibi-Robo, Starfy, Endless Ocean, and a slew of Japan-only releases that will probably never be released elsewhere. Considering how hit-and-miss new IPs can be, I'm not surprised Nintendo sticks with franchises they know will sell hugely.