This game is awesome. I played it for over five hours before I had a PS2, and I think it's a great sandbox style game. The new Harry Potter game tried to emulate it in every way and failed, which is too bad because the level of detail in Hogwarts is way higher than here. However, this game gives the player the freedom to determine his place at the school, and shape the outcome. I love that you live in a real and consistent world that has rules you must follow (see also: Shenmue, any MMO, most RPGs, and to a lesser extent, Metroid Prime). The interaction between a player and the world he lives in is paramount to the success of games that have strong narratives, and Bully (as well as the GTA series) do a fantastic job with this while giving you tons of freedom. The graphics could only get better on Wii, if they don't stay the same, and hopefully the control is awesome.
Based on the Manhunt and Table Tennis ports, I really doubt Rockstar is going about this half-assedly. We'll see though. I wouldn't be surprised if a GTA "Stories" game arrives on Wii. Personally, I don't want them to port GTA IV since it wouldn't play well, or would look terrible.