Below are the metacritic scores of the top 10 Gamecube and Wii third-party console exclusives. When adding up the score, you’ll notice that the Wii comes well ahead of the GC in terms of quality third party video game.
I’ve omitted and added a number of games, including Resident Evil 4 for the Gamecube (which wasn’t a third party GC exclusive in the previous generation, as it arrived on the PS2) and PGA Tour 10 Wii ( which was so fundamentally different from the other versions, that I consider it a Wii exclusive on the strength of its unique features).
Anyway, here are the games and their metacritic scores:
GC
Resident Evil – 91
Super Monkey Ball 2 – 87
Super Monkey Ball 1 - 87
Tales of Symphonia – 86
MGS: Twin Snakes – 85
Resident Evil Zero – 83
Final Fantasy: Crystal Chronicles – 80
Pacman Vs. - 78
Battalion Wars - 76
Baten Kaitos Origins - 75
Avg Score: 82.8
Wii
World of Goo – 94
Resident Evil 4: Wii – 91
Tiger Woods PGA Tour 10 - 88
Zack & Wiki – 87
Little King’s Story – 87
LostWinds: Winter of Melodias – 86
Boom Blox Bash Party – 86
Boom Blox – 85
No More Heroes – 83
Dead Space Extraction – 82
Avg Score: 86.9
That's pretty damn impressive considering the Wii is still in its infancy and the gaming press is biased against the system.
EDIT: Removed VJ from the GC list. I forgot it came out for the PS2. Added BW.
EDIT 2: Removed Ikaruga from the GC list. Added BK: 0