Should i get Super mario galaxy 2 or super mario galaxy?

Im getting a Wii for christmas , and i have some money to buy a game.
I was thinking of getting Super Mario Galaxy 2.. but i havent played Super Mario galaxy.
Should i get that one first? or just get Super mario galaxy 2 straight away?
Is supermario galaxy 2 wayy better ?
Thanks :)
Merry Christmas :)
6 answers 6