If a Nintendo exclusive is successful, it goes multiplatform or its sequel does. It never sells well on Sony or Microsoft
If a Microsoft/Sony exclusive is successful, Nintendo never gets a port or the sequel.
The Wii got exclusives because it was almost impossible to port games from the other consoles to it. Sony and Microsoft don't get exclusives unless they're first party or moneyhats, and in both cases it's pretty self-explanatory why Nintendo doesn't get the sequels.
It might just be that we read it quite differently, but that doesn't really rebut ShyGuy's point: if anything, it seems to support it. The expense and hassle of porting a Wii game to the HD systems was too much to bother with for most successful 360/PS3 games, but the reverse was apparently untrue.
Admittedly, this "analysis" hinges on my reading "Microsoft/Sony exclusive" as meaning "not-on-Wii game." I could well be wrong there, and appeal to the source for a definitive ruling!