Why would the game sell better on Wii in Japan?
Tales of Graces and Sengoku Musou 3 didn't exactly light up the charts compared to Tales of Vesperia (a port), Shin Sangoku Musou 6, and Gundam Musou 2.
The fanbases for old popular Japanese ps2 franchises seems to be split, with the majority going to ps3. The only exception seems to be Monster Hunter, but the franchise's popularity has grown immensely over the past couple of years due to the success of the PSP titles.
If FFXIII had been announced from the getgo for Wii, things would probably be different, but you might as well call the Wii the ps3 if you're going to change that many variables.