Galaxy 2 just looks like an expansion pack for the original - which I don't like - while NSMBWii looks like a rehash of the original - which I do like.
'I'd like to go with as little story as possible...I've always felt that the Mario games themselves aren't particularly suited to having a very heavy story.'
Okay, what mainstream Mario game before Galaxy had a deeper plot than 'save Princess Peach'? None of them. So it's no surprise, and I don't usually expect Mario games to have any sort of compelling story anyway. I've got lots of other games for that.
You were just talking about the possible story in Galaxy 2, and then you did a 180 and started talking about how you don't expect a compelling story from Mario games. While its true, Mario games aren't well known for their story, Galaxy is, so it only makes sense to assume that the sequel would at least attempt a similar story.
"Mario needs to save Princess Peach from Bowser, who's kidnapped her and is trying to take over/destroy/**** up Thing X. Some kind of Helper aids him on his way."
Galaxy is pretty cut-and-dry Mario, too. Rosalina adds SOME depth, but, not REALLY.
Circle of the Moon had a castle. Harmony of Dissonance had a castle. Order of Ecclesia, NO CASTLE. Castlevania Judgement..forget that, it's crap.
I was mentioning a possibility for Galaxy 2's story, but that doesn't mean I'll be looking forward to it. I still know it's ultimately going to boil down to 'save Princess Peach'. Again.