baloofarsan on 09 October 2016
I am not going to defend Metacritic but they are checking reviews every day. They have staff that probably want to make the site as reliable as possible.
If you really want to know how they calculate the scores you should read their FAQ:
http://www.metacritic.com/faq
http://www.metacritic.com/about-metascores
You can look at statistics for the individual reviewers (look below the review: "All this publication's reviews").
From a very quick check that I did it looks as if Nintendo-only sites are less biased than MS and Sony but I only looked at five of each.
