Im a simple man. I started rating things on a scale of 1-3.
A rating of 1 is something i watched/played/read and didnt like. Overall, i felt that the time i spent consuming the product was a waste of my time, and i will very rarely ever consume that product again. This would be games like Final Fantasy 13 or Anime like Phantom World.
A rating of 2 is something that, overall, i was okay with. It wasnt a waste of time, and at the end of it, i walk away happy. But ill still never play it again, and, in hindsight, probably wouldn't recommend to people easily. These would be games like Undertale, Just Cause 3 or Anime like Kabaneri of the Iron Fortress or One Punch Man.
A rating of 3 is something that i was also okay with, but at the end of the day, i look back on warmly, and generally would play, read or watch again if i felt like it. I would be more likely to recommend the product whole heartedly. Games include the likes of your Grand Theft Autos and Civilizations. Animes would include things like CLANNAD, SAO or Re;Zero.
Basically, its a No/Maybe/Yes system.
I keep the scores personally, because it helps me rewatch and replay more easily.