If it were possible, hell yes I would get it. The Cube, although it doesn't have a fast enough GPU, is the only 2nd Gen console to use an incredible type of mapping (bump or specular, I forget which). This mapping makes Prince of Persia the best visually out of the three versions. So, even though the game would never be possible, it would have some great effects that the others wouldn't.
I'm thinking maybe eventually another developer will get ahold of the GTA: VC or GTA3 license and port it to GC. However, they would have to strip something out, maybe some weapons, maybe some cars, and probably all of the extras like the minigames and the Arena. Also I'm sure hidden packages would be out, and probably outfit changes too. With all of this out, I'm sure VC would run on a Cube, although you'd have to downgrade a bit the quality of the textures.
Man, that's a lot of explaining for something that'll never happen.