It's all in the fine details you can focus on when you combine really good ideas and technologies. The Nintendo DS was successful because it was built upon excellent hardware and software, and Nintendo knows how to make things usable and fun. They also supported their developers well, and the library grew rapidly.

The iPhone is the same thing. Apple brought their usual level of fit and finish to the table, as well as lots of experience with portable industrial design, miniaturization, and fine materials.

Touch took so long to catch on because nobody did it right, plain and simple. The success of these devices isn't due to any one thing that you can just copy, and expect to succeed with. They succeeded because of a lot of effort and sacrifice, and decades of hindsight.