Mario Kart Wii!

Wii had amazing games, No More Heroes, Kirby's Epic Yarn and Wario Land Shake It are amazing games no one is going to mention. The best game though, or one of the biggest surprises the Wii has given me is DKC Returns. It took me by surprise. From the announcement, they team behind it, the looks... And then I tried it, expecting a similar gameplay to the SNES ones, and it was a perfect mix of good old gameplay and amazing new touches and ideas. Yes, Zelda SS and MP3 and Xeno are amazing games, but I think DK and Retro took the whole gen by surprise, and it's sales shows us that, more than 8 millions sold between Wii and 3DS port.

Skyward Sword

Followed closely by Metroid Other M, Xenoblade, MP Trilogy and Twilight Princess. What a heaven unlike the U.

Definitely Muramasa Demon Blade.  The 2D is just beautiful to look at most of the time. 

I give it to Xenoblade, but my 2nd would be Twilight Princess.

House of the Dead Overkill or Zack and Wiki.

I'm torn between Trauma Center, Radiant Dawn, or Fragile Dreams. TC was fun, challenging, and made excellent use of the wii mote/nunchuk, Radiant Dawn is the most epic FE game in the series, and Fragile Dreams is one of the most unique horror games I've ever played. So it's hard for me to pick...

Xenoblade Chronicles
Metroid Prime 3
Klonoa
The Last Story
Fragile Dreams.
Zack & Wiki
Muramasa
Rayman Origins
Boy and His Blob
Sonic Colors
RE4 Wii edition
Okami
Tatsunoko vs Capcom
Books Ys I & II
Nyxed Quest
Lost Winds

I haven't played every game in that list, but from the ones I've played: Monster Hunter Tri takes my vote. Quite possibly the best online experience the Wii had to offer, with terrific multiplayer, impressive presentation, addictive gameplay, and just tons of pure awesomeness.

Xenoblade is my favorite game on Wii and probably of all platforms (I think I'm spoiling the #1 game in my top 50 list XD). For me it was really mindblowing, even more than the first Mario Galaxy.