Why would they release it on Wii? Hell, why would they do a port, remake, or sequel period? It's a complete game; that ain't the point, though: the game tanked.
Why did they do one for Okami? It was a complete game and it didn't sell well. Granted that God Hand didn't get the critical praise it deserved like Okami, Capcom still saw it fit to re-release that on the Wii. Capcom also seems to be learning how to make quick cash on the Wii by porting old games and hoping for the best.
IIRC, it was Capcom's VP of business development who pitched the idea of Okami Wii to Ready At Dawn; the subtext in his blogged explanation was that Nintendo fans were demanding that Capcom do that very thing,
or else. Seriously, though, even the media were exclaiming how it'd be such a fab idea to port Okami despite Inaba's assurances to the contrary. The idea of using the Wii Remote as the celestial brush at least makes sense; the idea that God Hand's lightning-fast fighting mechanics can translate into sloppy motion controls is ludicrous. I've heard suggestions that waggle be used exclusively for the context-sensitive (circle button) actions a la RE4's knife-slashing, but ninfans apparently don't consider the fact that the Wii Remote/Nunchuck combo doesn't have two joysticks and that the evade stick
made God Hand.
Whatever the case, you are correct: God Hand's brilliant translation of the 2D beat 'em up to 3D didn't get the critical praise it deserved, so I doubt the (rare) calls for a God Hand port to Wii will be given the same consideration as those for Okami.
