Why is 2GB not enough?
Two reasons.
1) This is supposed to stay relevant for 6-10 years. Portable tech are getting significant upgrades every few years. Those things will be able to stream your game to your Big TV.
2) For many generations, it was all about the Graphics. I still think they can get better...but it didnt make a difference this generation. The big success early on was the Wii, with a new way to play, that made games more accessible. Nintendo threw it all away with lousy game lineups and insufficient 3rd party tools. I believe that the next big thing in games, is not graphics and not motion sensing, but AI. Like motion control, it can make games more accessible. But unlike motion control, advanced ai can appeal to hardcore crowd too. And game changing AI, will needs a lot of memory for the Models unless its all farmed out to the cloud. The kinds of things I am talking about need at least 2GB of memory on their own to offer anything remotely interesting.