first off approach was wrong,
pardon me, but i have the wii and have all 3 games and of the 3, super smash is the better overall game , but, may i ask, what age are you buying for and is it for a boy or a girl?
a girl who is 9? hmm, i'd go with either sonic or carnival games, of those she probably would like both, of the 2, mario & sonic is the better choice, also may i recommend either raymans raving rabbids or raymans raving rabbids tv party.
a boy 6-10? super smash, oh and does he like monsters? because there is an excellent game, just over there, called monster lab, he'd love that, he gets to build monsters of various types and adventure thru areas defeating other monsters in fights as he plays being a "mad scientist", extremely well done game and its only 40 dollars compared to the other games that are 50 dollars
do you have wiifit? you do? then tv party has games that use the board, also, see that shaun white snowboarding game? it is also excellent and would provide hours of entertainment for your entire family, it also uses the wiiboard.