It's common cents actually.
Nintendo has a really bad habit of miniaturizing
past technology. So games on its current handhelds resemble those on previous consoles.
But Sony has made their
existing technology portable.
"First and foremost, the PlayStation Portable is a portable handheld gaming device that really simulates the PlayStation 2 in the home." – Kaz Hirai, president and CEO of SCEA
"I think that a game like Headhunger: Redemption would look almost the same on PSP. It's very powerful. Also, you have less of a fill rate, so the graphics chip basically has the same capability as the PS2. I think we can do some hefty stuff on it. At first, when they were only going to have 8 megs of RAM, that was a hassle, but now that it has 32, it is the same as PS2." – John Kroknes, producer Headhunter: Redemption
So while Miyamoto & Co. were licking their chops and getting ready to milk another cash calf before bringing a cow to the dairy farm, Sony moved a step ahead of them, technologically speaking.
Besides, PSP's abilities (and rainbow of supported formats) suggests that there
IS something more potent than EE+GS inside ...