Too many to mention. Zelda: Twilight Princess, Excite Truck, Dragonball Z Budokai Tenkaichi 2, Surf's Up, Sims 2: Pets...
This title is the best launch title I have ever played, having missed Super Mario 64. It is not fun because it is an inherently excellent collection of games (I wouldn't call them minigames), but because the fun you have playing them with friends and family.
Using the WiiMotes really is as much fun as the online videos make it out to be. I'm a cynical die-hard gamer who has gamed since the Atari 2600 and I can tell you this little machine is like a whole new world to me. I love Golf. Golf! Why? Because every motion I make, heck even the stance I hold my arms at helps me to play the game better.
It is not true that the games have zero entry cost for none-gamers. Things like holding down a trigger button on the WiiMote to hold the bowling ball and then release to throw it take them a few turns, but get it they will and as soon as they hit some pins (which almost anyone can do) they start to enjoy themselves.
Bowling is the easiest game, and I think it is intentional. You have to work at missing pins unless there's a Spare to pick up - the game is how high you can score. Once you get beyond the basics, a whole world of "where should I hit the pins and from what angle and how hard?" opens up. It's truly great.
Tennis is also a blast, but my daughters can't figure it out. All I have to do is return the ball until they mess up.
Baseball is impossible; I need to read up on it. I haven't figured out how to hit the ball - it's not just swinging - you have to have aim the bat high to low. Pitching is easy and gives you four options on how to throw the ball, plus where ever you want to put it. It's just really hard to bat.
Golf is amazingly fun! It's got a lot of variety and holding your WiiMote properly and making a full arm motion works much better (for control of the force of your swing) than "toolboxing" it with your wrist.
Boxing is difficult but fun, unlike Baseball. I don't have two nunchucks so I haven't experienced multiplayer. It is the only game that requires a nunchuck in WiiSports.
WiiSports keeps track of each Mii's progress, and appears to have some kind of RPG stat system it keeps track of. The statistics don't affect the games, but do tell you "This Mii (and the person playing it) is better at Tennis than you are." I like it.
Maria, my oldest, can usually beat me at Bowling, but not every time.