Based on data pulled from GameRankings, folks over at GameFunk have prepared the nice little chart above. Apparently, Wii games don't get that great of marks from reviewers. Compared to the marks of games on other consoles, it makes the Wii's library look even worse!
Here's the numbers:
Xbox 360: 374 games: 26% good, 24% bad
PS3: 122 games: 33% good, 17% bad
Wii: 189 games: 11% good, 37% bad
But, before you punch your computer monitor in a fit of rage, know this: the Wii does have a lot of shovelware. It's just the price of success, as publishers and developers see the console as a means to make money. And that's what they're in it for.