Counting only Wii games (no VC, but yes WiiWare) I'd still take PS2 easily.
Right now, the overwhelming majority of top-notch Wii games are first-party, third-parties are just starting to figure out the console and develop good games for it. There's so many good third-party games that haven't come over to Wii or only came out as gimped ports (ie, where's the online). The best versions of Call of Duty, Dead Rising, NBA Live, etc were HD.
No matter how much more the Wii sells, because of it's technical limitations, I believe that there will always be games that are HD only. There was no such thing with the PS2, as it was the undisputed leader of the industry. Sure, there were some games that went Xbox/GC exclusive, but nowhere near as many that go HD exclusive right now.
The PS2 had every genre covered, and appealed to every gamer. The fact that it still sells almost as much as the PS3 is a testament to that, and I don't think the Wii will be able to keep up sales this far into the next generation.
# of games above 75 on Metacritic (including downloadable):
360: 241 DS: 144
PS3: 152 PSP: 126
Wii: 85