Just as a side note, Japaneese developers do not use "Game Engines" in the same way that western developers do ...
From my (very limited) understanding of the inner workings of Japaneese game developers, they tend to maintain a centralized code-base of loosely related libraries. The reason for this is that, unlike Wester Developers (who tend to focus on one or two closely related genres), many Japaneese developers work on a wide variety of games that (tend to) have very different technical requirements and they want added flexibility that wasn't available from game engines initially. This attitude is changing being that hardware has become powerful enough that you no longer need the performance benefits of custom software to make a decent looking game ... but I wouldn't be surprised if Nintendo was still working off of the library ideology.
With this in mind, I wouldn't be that surprised if Nintendo did or did not use Super Mario Sunshine as a base for Super Mario Galaxy ...
