if i were you i would bbuy mario galaxy as it's a great game and having great reviews... but if you're a fan of online play i think Medal of Honors 2 is a great online experience and be sure to get the zapper aswell as it fits perfectly with Medal of honors... but i also suggest getting super smash bros brawl as it's a gret gaame in which sakurai has put a lot of work into... Zela is a great game to start your wii experience with..
