i second mario kart 7 and pokemon x/y
resident evil: revelations is a great throwback to the older survival-horror RE games, also worth noting it's very fun with gyro controls (demo in the eshop)
if you like menu-based rpgs like final fantasy, bravely default is coming out in the us on february (demo in the eshop)
honorable mentions:
etrian odyssey (dungeon crawler franchise, may try your patience. demo in the eshop)
code of princess (fun arcade hack'n'slash that parodies other rpg games, marred by huge fps drops and virtually nonexistent balancing)