I wasn't aware of the Metacritic scores (surprised), but I'm inclined to think that's just a very interesting coincidence in this particular instance.
I don't think anyone is buying the PS4 because they're looking at Metacritic and thinking "Which new system has the highest number of games rated above X percentage because that's what I'm going to buy."
Personally, I'm inclined to think the PS4 is selling upon the momentum that started with their strong debut which was aided by a favorable price to performance perception, a "consumer favorable" perception and the most favorable press heading into its release. That's for consumers who were on the fence as to which new system to buy; brand loyalists, who are often early adopters, are easy enough to predict, but do not determine runaway sales when one product outsells the competition significantly.







