Our mean average for all editor-reviewed scores is an 81%, according to GameRankings.
I think we're up-front in that we use a school-based grading system. Maybe half the numbers are "wasted," but in a school setting, how often do people get less than a 60% for their overall output in a year? Very, very few people. And they tend to drop out.
Similarly, most games that WOULD deserve a score that is failing (50% or below) probably get thrown aside before ever making it to published status.
Anyway, I think it was Hathen who said he's only seen a few under 50% scores, and from people who don't work here anymore. A quick check netted me these:
http://www.rpgfan.com/reviews/digimonworld-datasquad/index.html -- 35%, written by me.
http://www.rpgfan.com/reviews/manakhemia-psp/index.html -- 43%, by John McCarroll.
http://www.rpgfan.com/reviews/deeplabyrinth/index.html - 48%, John McCarroll.
http://www.rpgfan.com/reviews/Flower_Sun_and_Rain/index.html -- 40%, Kyle Miller.
http://www.rpgfan.com/reviews/Heroes_of_Mana/index.html -- 46%, me.
http://www.rpgfan.com/reviews/myst-ds/index.html -- 45%, me.
http://www.rpgfan.com/reviews/ff2anniversary/index.html -- though 58% overall, an awesomely-low 5% story score. From Ashton Liu.
Those were all written in the last 3 years, most of them in 2009. And all by current staff.
You see we don't really go under the 40% mark. But if you know of an RPG that you really think blows so hard as to belong in the 0-30% range, please tell us the name and I'll happily play enough of it to agree with you and write the review. Lord knows there are some free-to-play MMOs out there that deserve it...I just can't stomach the thought of sinking time into them.
Regarding grading philosophy in general, our take is that if a game makes it to market, it will generally have SOMETHING of redeeming value to it. Someone can find something to like. A game that gets under 50% means it's SO bad or SO broken that no one can enjoy it. NO ONE. There are very few games that meet that criteria, don't you think?
Ramza