The answer is in the title...
There is currently no Super Mario Galaxy 3. If you mean Super Mario Galaxy 2 there are 242 stars.
Super Mario galaxy 2 can be played as a 1 or 2 player game. You can play with 2 players simply by plugging in another wii remote. When you play with 2 players, player 1 steers Mario, and the other a luma. The luma can stop enemies in their tracks and then spin to make them fall over. Player 2 can in addition pick up coins and starbits. Also if both players point at Mario at the same time and press the A button at the same time, he does a super jump.
42
$40
Super Mario Galaxy 2 will be released in the US on May 23rd 2010.
6 stars
to be honest......none
there are 49 Galaxy's including the grand master galaxy
8 files of choice.
Billions and Billions ,then, infinaty
7 times you must lose a life in the galaxy and then the super guide engages.