Personally, I would love it if they rescued Banjo-Kazooie. The first two games in the series are close to perfection, and it would be great to see what the talented minds at Nintendo EAD could do with the property. Banjo-Tooie, with it's expansive environments and physically connected levels, hinted at a bold future for open world platformers. So far that future has gone unrealized.
In terms of benefit to the industry, it would make most sense for Nintendo to pick up Mega Man, a founding father of the modern video game industry. The series could make a return to its former glory under the watchful eye of Nintendo EAD and/or Retro, two of the best platform developers out there.
If it's about turning a profit, it would make sense for Nintendo to buy Monster Hunter and ensure exclusive rights in perpetuity.
