It's true, Sony could develop a portable PSOne, but I would be concerned about the size. My guess is it would be at least 6.5"x5"x1.5", and last maybe 3 hours per charge max. Not exactly shirt-pocket material; mainly because they're limited by the size of a CD. Nintendo could probably...
An update on the N-Gage - Nokia Europe reps, when asked about the price of the unit, said it would debut at under 500 Euros. So who wants to shell out $499 for Nokia's GBA eater?
Joe, the backbone of your argument has been Nintendo's proprietary mini-DVDs and high licensing costs. Unfortunately, it seems the Cube's licensing costs are on par with the PS2. The fact that the Xbox undercuts them both is because Microsoft often pours illustrious amounts of money at their pet...