Resident Evil 4: Wii Edition. They claim to have shipped over one million copies of the survival-horror game worldwide. Of course, 'shipped' does not mean 'sold', but we can at least assume that the majority of these discs have found their way into homes, unless Capcom 'shipped' a few hundred thousand copies into their own Sales Inflation Warehouse.
This should remove any lingering doubt as to the motivation behind the Okami port, since Capcom has discovered that old games can do excellent business on the Wii, while saving on annoying costs like development. We should look forward to the inevitable rush of PS2 and Wii ports, as companies mine every old game that seems the least bit viable. And also Ninjabread Man.