Quality... that is what I feared... there we go again !
IMO if you consider Metacritic scores, they have to be considered by plateform only.
You don't compare the general score of the 360 vs PS3 like you wouldn't compare the score of the ps3 vs the DS..
EX: A given game on a given console might have a great score because the console "would" lack of that kind of genre particulary.
While games on the other plateform would get a lower score because the catalogue for that same genre is already in good supply.To me a Halo Wars got an ok score because it suffered from the C&C competition already, otherwise it would have reached the 90% no problem.
To me, this kind of calulaction is biased and doesn't make sens UNLESS if you calculate a "weighting" (not sure it is the right word in english) over the total score generated over the entire catalogue of games.
... otherwise it is biased "statisctics" and you reach any conclusions regarding your preferencez or whatever you are trying to prove... 
Evan Wells (Uncharted 2): I think the differences that you see between any two games has much more to do with the developer than whether it’s on the Xbox or PS3.
