As time goes on expectations change and reviewers usually are less affected by market hype. For example I don't think games like Halo 3, Gears of War or Mass Effect would score that well if they would be released unchanged at the end of this generation of consoles.
Also there are different expectations for different platforms, if a PS3 or 360 game would look like a Wii or PS2 game this would be heavily punished, while if the game would be exactly the same on the PS2 or Wii the game may receive much praise.
Hypothetically it would be nice if at the end of this generation there would somehow be an ability to re-review the games with the reviewers don't knowing the exact timeframe, marketing or target platform of the game they are dealing with to get to more objective conclusions.







