Its some people that dont want Halo4 to be on top of the "charts". Same happened to Inception its not the best movie ever but for a period of time it only had perfect reviews on IMDB and was like 10% below what the average score was. Makes no sense.
Its like some people want to defend the top 5 spots from new games/movies etc. And when the "bad" reviews show up it magically corrects itself.