Personally, I think it would have sold much better than it currently has.
1. It was originally released on the ps2 with little to no marketing amongst a plethora of other titles. Given it's odd art style, it was ultimately ignored by 99.9% of ps2 owners.
2. It was re-released on the Wii with no improvements whatsoever outside of the controls, and it was released after TP, SMG, MP3, SSBB, and Mario Kart Wii, and thus was once again ignored by the populous at large.
3. Had it been a Wii launch title, it would've been the only really good "core" title for the Wii aside from TP for almost an entire year (though some might complain about two very similar games releasing in such close proximity to each other), and it probably would've sold pretty well as a result. Also, Clover would've had an extra seven months to optimize the game for the Wii, improving not just the controls but also the visuals, giving the game a nice extra coat of paint over and above what it had already recieved. This version would've been superior to either version currently released, and the game was practically destined for the Wii in the first place, as shown by the Wii port's excellent controls.
If this game had been a Wii launch title, it would've done much better than it did on the ps2, and later on the Wii. For all we know, Clover might still be around and an Okami 2 could be in the works.
If only Capcom had forseen the success of the Wii... :(
Edit: To clarify, I'm saying if they had delayed the ps2 version to make it a Wii launch title, then the above may have happened. As in, had they not released it on the ps2 at all, and just went straight for the Wii.
