While things like Metacritic are far from perfect, I think its a shame more people don't pay attention to it. The great thing I like about Metacritic is that it takes all the marketing, trailers and preconceived notion about it and gives you a generally quite clear cut "yay or nay", based on things that you couldn't possibly know before playing the game. That way, on Metacritic a good indie game like World of Goo or Braid will get the same seal of approval as, say, Mass Effect 2 or Bioshock.
While this probably doesn't make a massive difference to the AAA titles, I'm guessing it does bring needed attention to some of the more obscure indie titles.