10 - PERFECT - No anime is perfect objectively, of course. The 'flaws' considered by others do not concern me in the slightest, I love every moment of it, and either the series or one of the characters in it, is on my favorite list. I can easily re-watch series with this grade and I'm always recommending these shows to other people. They are the reason I watch anime in the first place, to find more such shows.
9 - GREAT - Amazing series with a minor complaint or two. Extremely enjoyable, would re-watch it with maybe skipping through some unimportant scenes. Highly recommending anime with this rating.
8 - VERY GOOD - Good quality show, what should be the standard of every series worth investing time. Mostly re-watchable, unless it's an anomaly in a disliked genre. From here on and upward, I usually recommend such anime to my acquaintances.
7 - GOOD - A satisfying series with some medium flaws. Certain scenes are re-watchable, but not the anime itself, unless it's to my taste. It is the most common grade of finished shows. I never drop anime with this and above this rating.
6 - OKAY - I can usually predict what will happen, or it's oscillating from being boring and not boring, hence it heavily depends on whether it will improve. From here on and below, there's an ever-increasing chance of me dropping the show.
5 - AVERAGE - It's either mediocre throughout, or at first good then bad. If I finish it, I regret watching it. When I drop it, it's because it's not worth my time.
4 - SUB-PAR - Not only I'm not getting anything out of it, I actually feel it's a chore investing any time into it. Either that, or it had a major screw-up during the series. (usually dropped before or up to middle of the series) It is the most common grade of dropped shows.
3 - BAD - It never succeeded to be enjoyable whatsoever. If prior's not the case, anime is most likely really nonsensical. I never complete anime with this and below this rating.
2 - REALLY BAD - It's the epitome of boredom OR cringe, there's nothing worse than watching an anime which is nauseatingly boring. I usually drop the anime around second/third episode.
1 - ATROCIOUS - Dull, contrived, stupid AND most of all, unlikable. Represents everything I hate in the medium. Usually the atmosphere is so fake, it makes me puke, and I can't find a single good quality about the show. Ironically, these are hardest to find, but it never makes me want to find more. I linger around wondering how bad can it get, but I soon realize there's no point.