It seems Nintendo will be taking a more simplified, classic approach to level navigation in Super Mario Galaxy 2: unlike its predecessor, there won't be a hub world. Game Informer reports that like New Super Mario Bros. Wii and so many 2D Mario titles before it, SMG2 is going the "world map" route.
"We want players to focus on the joy of the action instead of getting to each game course," said famed designer Shigeru Miyamoto. "We wanted to make it as accessible as possible and as easy as possible for the players."
"Also, because we're going to incorporate a number of different stars and conquering all the stars is going to be one of the most challenging missions for the player, we want them to understand as easy as possible where they should go next and which places they should go back to in order to get access to the remaining stars."
I wasn't particularly fond of Super Mario Galaxy's hub world, and the same could be said of New SMB Wii's world map. I like either approach when they feel inspired and imaginative; it's as simple as that. Good examples of this include the Donkey Kong Country games as well as the Banjo-Kazooie series.