Sonic Generations didn't make it to the Wii as well as Sonic CD. Sega wanted the game to be in HD, so they didn't release it for the Wii. It has been quite awhile since it has been mentioned but I still need to mention it. So basicly they only wanted the game to be in HD, not to take fans back with a nostalgic ride or something. I mean, some Sonic fans only own Wii consoles so they could be sad all over because they can't own other consoles.
Maybe it could be the 3D
All the versions of Sonic Generations are playable in 3D, that's why it is on the Nintendo 3DS. Could it be that because the Wii can't support 3D as well. But it seems to be the HD that the game is not for the Wii. Anyway, does anyone still want it on Wii? Normally, yes, right?