It depends...
Metroid Prime for example appeals to a similar demographic like Bioshock; MP sold about 2.8mil on GC whereas Bioshock sold about 3.8 on 360+PS3. If MP would've been released on 360+PS3, it would have had probably sales somewhere like that. So, yeah, it would have sold more, but considering the install base, the difference is not significant.
The point is: Nintendo consoles are almost completly bought by the demographic that buys Nintendo games. On other consoles this demographic is rather small thus there wouldn't be such a huge increase in sales. There might be some exceptions for this theory, though. I don't know how huge offline multiplayer is on non Nintendo consoles - games like Mario Kart or Smash Bros. would sell huge, but actually they sell already decent on Nintendo consoles.
In the end, I don't see a point for Nintendo to stop their hardware business and go software only.
bizarre-galaxy.de - My Browsergame, but sadly only in german :(
You can play as an octopus, though!
