My basic attitude is that unless reviewers and critics can be detached entirely from the industry creating the games any kind of score is meaningless since at the end of the day they have to worry about their jobs and the industry being willing to send them more games to review.
That said the most important point I think is for reviewers to be consistent with all their reviews. Meaning that in reviewing a game now, it should be viewed not in the context of only the games coming out right them, or on the market recently, but in the context of every game the reviewer has played. Something increasingly important as gamers themselves have been at this for increasing amounts of time and can have very wide perspectives. Let's say your reviewing a first person shooter or dungeon crawling RPG, in assigning a review number you should consider it in comparison of other games of the same type. Does this game your playing now measure up to how good a game of the same type you played 10 years ago? If say you think Wolfenstein 3D was better for it's day (important qualification) than the current Wolfenstein is for today that should be in the review, if you happened to think say "Shadowcaster" or "Cybermage: Darklight Awakening" innovated more than a current first person shooter that should also figure. In short, especially in this stagnant industry, I think it's become increasingly important that developers compare themselves against all the games that were as opposed to entirely what's being done now. This means that some old grognard actually qualified to be a reviewer might wind up calling all games today crap compared to what he played in the 1990s because the innovation and a lot of the depth is gone, replaced entirely by graphics and sound in many cases. Being called on this is important. What's more the odd thing is I think a lot of graphics today are lacking compared to the 1990s where people did the best they could usually and the games looked great for their time, today it seems like even in terms of graphics and sound we're seeing them cut back due to things like Ubisoft's 30fps cap and things like that, basically you didn't see games in the 1990s saying "well yeah, we could do better graphics but it's more cinematic to release in 16 color EGA as opposed to this new fangled 256 color VGA stuff... and forget Sound Blaster, the PC speaker might make your ears bleed but it's more immersive that way".