Having only bought the Wii a couple months ago, I'm still fairly new. This game came with my console and I'm so glad for it because it still has yet to be surpassed as #1 on my list. Sure, there's not a huge plot or great depth to this game, but when you just want a quick hour or so of fun this game is perfect.
The games can be played solo up to four players including training mode. I usually play in training mode when it's just me and play the actual games when I have a partner. For one person, my favorite is bowling. Out of all the games, I would say it's the most realistic with controls because you can move your Mii and angle the Wii remote to make the ball hook. For multiplayer, I like tennis. With this game you can either be on the same team or compete against each other. You can even be on both teams, but that's a little too confusing for me.
Although I usually do training mode solo, it's also a lot of fun to compete against someone else because you can try to beat each other's scores. I find golf (target practice) and baseball (home run derby) to be the most fun when you're playing for top scores.
Finally, there's a mode for finding out your Wii age. This is basically a test of three different training games, and it will only test you on the training games you've already tried. This is okay if you want to see where you are and keep track of how your "age" changes, but I don't think much about it and often forget that feature is there.
Overall, this is really a fun and simple game for all ages, friends, and family. I usually pair this up with Wii Fit for a little extra activity and variety.