My point was that X-Play scores on a scale of 1 throgh 5 stars with no half scores. The lowest 7.5% of the Wii games have gotten 1 star which is translated as a score of 20. If you look at Metacritic average for the lowest 7.5% of the Wii games that are also reviewed by X-Play, the average score is about 42 (they are not the same games, but you get the point). Therefore if a game is bad, X-Play, because of the way their scoring system is set up, will likely rate it 22 points below Metacritic average. Conversley, they have rated the highest 7.5% of Wii games 5 stars, which is a score of 100, Metacritic average for the highest 7.5% games is 93, therefore X-Play will likely rate the highest games 7 points above Metacritic average score. It's because of the wasy the scores are set up.
This is different than what I was initially thinking with Wii games being two camps and HD more of a spectrum. That was just speculation, this is data.
As to why the Wii games scoring less than Metacritic average lately, there is a simple ans more innocent explation than X-Play trying to sabotage the Wii. The games on the Wii lately have been below average in general, and those games are precisely where X-Play will below Meacritic average because they will hand out 1 and 2 stars while the averages will be 40% and 55% for the same games.