While I love RottenTomatoes for Movies, I find it abysmal for TV Shows. Here are some shows with a >90% score:

- Almost all seasons of Supernatural

- Seasons 3 & 4 of Veep

- Seasons 4, 5 & 7 of New Girl

- Season 2 of The Flash

- Season 2-4 of Arrow

Now I'm not saying that those shows are all shit (tho they are certainly not in my ballpark), but I doubt anyone thinks of them as 100% shows, in the same sense that Moonlight is a 98% movie.

The problem comes with few reviews (which is also a thing with more niche-y movies), which is probably amplified in later seasons, where reviewers who don't like it stopped watching.