Super Mario 64 was just hub worlds, right? Same as Super Mario Galaxy? I forget what Super Mario Sunshine was like. They should just do an actual open world like Jak and Daxter, where you move seamlessly from area/world to area/world like they're physically located next to one another.
Sunshine was a little more open just in that the "hub world" was pretty extensive. But you still went into portals to go to the "levels". Those were more like 64, though, in that you had many objectives in each one. They do that a little
in the Mario Galaxy games (with 2 or 3 stars and other challenges in some of them). But also in both of those games most of the levels themselves were more open. Much of Mario Galaxy is linear - there wasn't a great deal of exploration within each level. I think that's what we are talking about when we say return to that style.
But yeah, a completely open world with tons of collectibles and secrets to find would be awesome. That kind of game takes a while to put together, though, especially with it being a departure from what they are used to. I wouldn't want them rushing something like that out for this Fall just
to have a 3D Mario on the market. That almost makes me thing that if they really are going to push something out it will probably just be another Mario Galaxy. Hopefully we'll find out soon!