This is Mario's most amazingly displayed adventure ever.
At the beginning of the game you gain an ability that allows you to do a second jump in mid air. Although it is a nice feature to have, it made the game a little bit too easy. It is very similar to F.L.U.D.D. 's hover nozzle from Super Mario Sunshine but that is no comparison. My point is that F.L.U.D.D.'s nozzle was necessary in order to beat the game. To get to point B from point A Mario had to jump and then use the hover nozzle. While in Mario Galaxy the second jump was not needed to get anywhere. Their is always an alternate route that does not require the double jump.
Another strong element that I felt was missing was the lack of adventure on the level choice planet. In Mario 64 their were hidden clues in the castle that you had to search around to find. Same in Super Mario Sunshine. Although it is located in a city, the city has secrets to it that you must complete in order to get all of the shine sprites. Mario Galaxy lacked this. Although their were hidden plants from the hungry luma, it still lacked the mystery of trying to find every single star. All the stars are mapped out for you, with one exception. On one of the planets that are single event and one star opportunities their is a hidden green star. But that is only on one planet.
As the 3D Mario plat-former series goes along it starts lacking its sense of adventure. In Mario 64 you would wander around the castle looking for new paintings to jump into. The fact of finding one made me happy. Sunshine was very similar except it was easier to find the levels. But in galaxy this was all lost. All the levels were mapped out for you and making it impossible for you to miss one. I did not like this. They should have either changed it to an individual galaxy hidden around the level choice planet. Or they could have kept the same system that they have right now and every time one would pick a new level Mario would have to fly to the level in the "Mushroom Brigade." Very similar to flying to new planets in the Kingdom Hearts Series.
I guess my point is that Mario is starting to lose what makes it Mario. I need the hidden secrets and hidden levels in order for the game to be completely enjoyable and it cannot be too easy. Other than these small details of the game, it is the best and most entertaining Mario adventure and revolutionizes the plat-former genre.