It depends on who and how many will be using it, Lefty. Here, 4 controllers and 4 nunchucks were essential. You can have up to 4 players for Wii Sports, and we usually do. That's a good game, along with the Super Mario games, for pretty much everyone. There are the sports games that are very popular with men. There are first person shooters, which lots of kids like. There are RPG games, which I personally love, but they are games that you work through to an end - called beating the game. Those have a different pace - you either like them or you don't. There are driving games and fighting games and music games and fitness games.
I would suggest going to GameStop, or some place similar, where you can try out games there. Also, ask your daughter. She's 12, right? Also, you can rent games at BlockBuster which is a very, very good idea. The games are expensive and sometimes they aren't games you want to play more than once so renting is the cheapest way to decide what you like.
BTW, I love Wii Fit and your wife might, too. It has an awesome yoga section, it weighs you, and it's a lot of fun for an adult. My kids liked it for a while but it really doesn't keep a kid's attention.