It's not simply marketing that sells the iPhone. It also has a slick, innovative, and simple UI, which allows it to attract people who are otherwise intimidated by smartphones. In fact, there was an article a few weeks ago that discussed how the general consumer is turned off by the complexity of most smartphones. Surely, the N series phones can do just as much as an iPhone, but the learning curve is much higher and requires more a tech savvy consumer. In the US, in particular, the N series phones are not offered by any carrier, so that limits market penetration.