The guys at IGN have posted an intriguing article about the evolution of portable gaming units, from its early beginnings to what it has morphed into today.
The gaming industry continues to gain speed, and we as a community are entering into yet another generation. We continue the progression from system to system, technology to technology, and innovation to innovation. No matter what console may be hitting shelves soon, there is already another in the future for us to look forward to. This industry has yet to be stagnant since its birth over two decades ago. When looking at the industry that publishers, developers and consumers have created, one can't help but be amazed. Gaming is a worldwide phenomenon. Gaining as much attention as Hollywood itself, society now considers our pasttime a legitimate form of true entertainment and consumerism. Within the juggernaut of our fine industry, there are subcultures. The console and handheld markets have always remained separate. There are times, of course, when one crosses to the other (such as GBA to GameCube connectivity, or PSP's progression into "portable console" territory), but above all, the industry operates as a two-sided coin.