As you can see, despite having a library of only around 30 titles by Nov 1 after launch, the N64 had approximately the same number of 80+ and 85+ titles as the Wii! What other mainstream console has such a poorly rated 1st-year library? My guess is that the Saturn's library rates very poorly, but it's not on Metacritic. But as you can see here, the Wii has the worst-rated year 1 library of any console in recent memory.
That raises a couple of questions.
1) Why is the wii library received poorly by critics?
2) Will that change?
Personally I think there's a few factors resulting in the low reviews.
a)Waggle is still an experiment for developers.
b)Nintendo was really harping on low development costs so they are getting games with low development costs.
c)Expectations have risen due to competition. The Wii is a relatively small jump in performance compared to the last gen.
d)Developers weren't really expecting to support the wii but decided to throw out a half assed effort because of its reception by the public.
I don't doubt there will be 'more' effort put on wii titles, but I think they will probably always lag behind a bit in reviews because of expectations and competition. I'm not sure you'll ever see the effort of an Assassin's Creed for the wii.