Lets find some unknown good games on the Wii(lots of media)

[Gamerace]

Mercury Meltdown, Kororinpa (tilt games, great)
Elebits - novel gameplay
Let's Tap - Really novel and fun game
Ivy the Kiwi - great overlooked game
Fishing Resort - extremely deep fishing game
Lost in Shadow - Unique platformer
Sakarua Wars: So Long my Love - Awesome romance SRPG mash-up. Only game of this type ever to make it out of Japan
Sky Crawlers: Innocent Aces - Best flight Sim - good luck finding it now.
Tenchu 4 - stealth ninja action
Project Zero 2 (in PAL regions) - horror
The Calling (horror)
Cursed Mountain (novel horror on a mountain with tibetan monk ghosts)
Ghostbusters
Trackmania - intense racer - build your own tracks
Prof. Wolfe's Gravity (physics puzzler)
Sam & Max (1&2), Broken Sword, Secret Files (1&2), Tales of Monkey Island (1-5 on Wiiware) - Point and click gold


Already mentioned I second:
Opoona
Munchables
Mushroom Men
A Boy and His Blob
Rogue Trooper
Fragile

Other more 'known':
Prince of Persia - Forgotten Sands
Lara Croft: Anniversary
Go Vacation