The following scores are “good” through September 29th, 2021.
There is a healthy fight within the stat community on which quarterback metric is most coherent. Passer rating is bashed as too antiquated. When used to compare quarterbacks from eras of yesteryear, passer rating is indeed skewed and inflated. But touchdowns, passing yards, interception, and completion percentage will never be wholly irrelevant.
ESPN’s QBR is said to factor in more intangible-type ratings. It can be interpreted as a more detailed and comprehensive version of passer rating and then some.
Pro Football Focus uses its grading system to assess the x’s and o’s of each game and pump out a yearly score.