Goldeneye 007 - a cracking game, unfortunately a distant relative to the N64 version but as a game in itself, brilliant. I've put in 28 hours on multiplayer alone.
Resident Evil 4 - the Wii controls really push this game to a new level and is just so immersive.
Legend of Zelda: Twilight Princess - I've never really liked the Zelda series, but found myself really investing the hours into this game. If you've played a Zelda game, you know what to expect.
Guitar Hero - They're just fun.
Dead Rising: Chop Til You Drop - Wii version of the XBox 360 game, surprisingly good. If you hadn't played the original version, you wouldn't notice that there isn't a world record breaking flashmob of zombies around every corner. There are still enough zombies to make you very nervous.
No More Heroes - Not the longest or most complex game, but I thought the style was great and it all looked mad. The artwork is sexy good looking too.
Warioware: Smooth Moves - Party micro games that are really really fun. With a group of friends, the action is hilarious. The dancing minigame is especially worth tolerating other people handling your controllers without first wiping the salsa off their fingers.
BAD GAMES
So many, because the Wii requires less development than the other consoles so it is crammed with crappy games. Check the supermarket's bargain bin for examples. Anything that is a cross-platform game usually tied in with a movie release is prime suspect.
Red Steel - Should have been so good, the idea of being able to wield a gun and a sword is pant-wettingly exciting. Unfortunately suffered from being the first out of the gate when the Wii was released and the development to make it perfect was lost. Didn't hit the right note with the sequel either.
Wii Beach Sports - Bowling, golf, table tennis, on a beach! Yeah, another repackaging of existing material from Wii Sports and Wii Play to showcase Wii Motion Plus capabilities. It's expected of Nintendo to dust off old work they did before, give it a little tweak with a new cover and hope no-one notices i.e. the "Stephen King Process".