I'm not sure they bought exclusivity to RE4. My understandng was they moved RE to the Cube because they were building stronger relations with Nintendo, and the Cube was a more powerful system than the PS2 (for obvious reasons, XBox was not considered).
If anyone can confirm that they did or did not pay for this support, it would be appreciated.
As for buying Wii support, why bother? They have the best selling console in all regions. The games are much easier and cheaper to develop. Lower cost + higher user base = $$$$. Why should they add more to the pile?
That's not to say that they shouldn't go out of their way to encourage support. Better access to development tools, advisors for implementing the Wii, Mii usage, even renting/loaning out franchise mascots (ala Link in Soul Caliber). I'd also offer free demo downloads via the VC for any game that meets a certain "quality threshold" - imagine how that could have helped the sales of Zack and Wiki!
