In a style very reminiscent of Sock Master's Game Console Controller Family Tree (from which, the author admits, he draws inspiration), Daveynin has compiled a similar family tree for the history of the portable console. Starting with 1979's Microvision (sorry, Game-and-Watch, enthusiast, his tree only pertains to cartridge-based systems) and continuing all the through 2005, is pretty thorough and easy to read. Each console has been color-coded by region and arrows provide relational connections, and each image links to its respective Wikipedia entry. It's definitely worth a look.
