I can't fathom people being excited about a possible Mario Sunshine HD remake, I hated that game so much :/
It seems that few people liked that game. The atmosphere is just so charming that I can't help but loving it. The soundtrack is memorable and some levels were downright gorgeous (Noki Bay comes to mind). Plus that water effect...
They would have to rethink the whole "blue coins" system in order for it to be even remotely interesting though.