I think I've figured out where the percentages rank if anyone cares:
70% is above average. Definitely more liked than loathed, but unless it's a weak year, no chance of making the postseason. Liv Tyler, Elisha Cuthbert, Charlize Theron, Kristen Bell, etc.
75% is good. Good shot of making the postseason, but not necessarily a given because it could be a strong year with lots of GBOWs in that range.
80% is elite. Kate Beckinsale, Yvonne Strahovski, Jessica Alba, Summer Glau, etc. Of course, that doesn't mean anything in the playoffs when an elite (Alyssa Milano) lost to a good (Angelina Jolie) in the first round.
90% is hall of fame. Only two GBOWs have ever made it that high so far.