It is a crying shame that the N64 ended up being the last cart based game console. I know that DVDs, CDs, and now Blu-Ray can hold more game data, but I love my cart based games. Too bad that there will probably never be another one.
Apart from handhelds, it's still the ideal format for them. I think sony were sticking their neck out with the PSP; optical media isnt really very good at coping with mobility, its the nature of the beast. That said, sony's personal CD players were pretty successful, as were other manufacturers'.