I honestly don't think many of their own dormant IP's are worth that much. Well, these are what I think would be worth buying:
Timesplitters. I know Crytek owns that now, but when it was available (and it may still be for sale, you never know) it would have been a perfect fit as Nintendo need to disrupt FPS's, third parties don't seem to be trying hard enough, and it already has a good presence among Nintendo fans.
Burnout. EA seem to have sidelined this in favor of Need for Speed. Burnout did well on the GC, and Nintendo are in need of a good racer that's not a Kart Racer.
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.