It may look and feel much like the first Mario Galaxy, but it's still a great game and a must have for Wii owners.
The story seems much like the last Mario Galaxy or any other Mario game ever. The Princess is kidnapped by Bowser and Mario must save her. Bowser is once again using the Power Stars and you must collect these stars by beating levels. The more stars you collect the closer you get to facing Bowser.
New to this game is the addition of Yoshi. Now he isnt in the game alot but when he is its very fun and makes you wish you could use him more often. You can also play as Luigin in certain levels. Luigi was unlocked in the first MG by collecting all of the stars. In this game however certain levels will start off and you can talk to Luigi. You can play as him or continue as Mario. Eventually every level is playable as Luigi. The new power ups include, a ghost suit, allowing you to go through walls, an Ice flower, allowing you to shoot ice and run on water, a fire flower which is just like the classic Mario games, you shoot fireballs. There is also the Bee mario suit which allows you to fly and climb on honey. Some of these power ups might have been in MG1, but these games feel so similar that it all blurrs together to me.
All in all the difference between Mario Galaxy and Mario Galaxy 2 isnt very big but these games are great. The levels change enough to justify buying each one. In all honesty I cant tell what levels were in each one because of how similar each game is. Some people feel its too much of the same thing, but if it's not broke dont fix it, right? To me this is not a bad thing.