I realize this will be subjective to the persons involved but, as it may come up down the road. This is the ratings system I use for movies to games.

1. ‘Do Not Want’
God awful, makes you want to gouge your eyeballs out with a spork, and either headbutt the TV or try to hit the cinema screen with projectile vomit. Everything about this movie/series is bad to such a degree that it doesn't even become good in its badness. You really wish you had done something more worthwhile during the movie's running time, like trimming your nose hairs. If someone would give you this movie/series, you would microwave, burn, blend or eat it, to avoid the risk that other human beings could be exposed to it.
2. ‘Awful’
Still awful, but has at least one thing that is done well, like one decent scare in an otherwise pathetic horror movie/series, one good laugh in an otherwise decidedly unfunny comedy, one clever plot element, etc. You would never ever want to watch this again except maybe for that single good part.
3. ‘Bad’
Bad, but you agree that watching this film was an OK pastime on a lazy weekend evening because there was nothing else on TV and you were too lazy to dig up anything better. Or, you felt the need to expose yourself to something crappy to recalibrate your appreciation for movie/series, and without being a totally shameful waste of time it reminded you how bad a movie/series can be. You could have better spent your time, though. You will definitely avoid watching it again, even on the next lazy weekend evening.
4. ‘Nice Try, But No Cigar’
Still bad, but is ‘almost there’. Either it has some good parts that are ruined by bad parts, or it stays at a constant level of “it had promise but the good part never came”. You still would never want to watch it again.
5. ‘Meh’
The threshold for ‘OK’. It's not good, not bad, just acceptable. This is the kind of movie/series that only just makes you feel you didn't waste 90+ minutes. You would only want to watch it again under the conditions of 3, but you would never ever consider doing more effort than pushing a button on your TV remote to watch it again. This movie is either an equal mix of good and bad parts, or is just so forgettable that each time someone mentions the title, you need to read the plot and look at screenshots to remember what it was about. If you would be given this movie/series as a present, you would sell it or give it away.
6. ‘Not Bad’
It has some aspects that lift it above mediocrity and make it quite enjoyable to watch, but it either never becomes really good, or if it does, it still has some bad parts that drag it down. You would only watch it again spontaneously if it were a long time ago since you saw it and you re-watched all your movies scoring 7+ too recently. You would only recommend this to someone if they're really into the genre, but you would still warn them that it's not that good. You would never buy it, but if someone would give it to you, you wouldn't bother selling it unless you need to make room or are in desperate need to gain a few bucks.
7. ‘Good’
This movie/series is really worth watching and you would watch it again spontaneously, but not too often. It's just not that good that you would say to your friends that they would really miss out on something if they didn't watch it. It's very enjoyable despite some noticeably uninteresting parts, subpar acting, plot holes or other negative points that you'll always remember when thinking about this movie/series. If you would find it in the bargain bin of your media store for a bottom price, you might buy it.
8. ‘Very good’
This is the kind of movie/series that you could watch again several times, even though it is clearly not perfect. There are still some minuses about this movie/series, but the rest is good enough to almost forget those. You would recommend it to friends unless you know it's not their cup of tea. You would be prepared to pay the normal price in the media store, or buy it immediately if it's discounted.
9. ‘Excellent’
It's almost perfect. You could watch this movie/series again almost an unlimited number of times. It still has something significant you don't like, therefore you don't give it an outright 10. You would recommend this movie to your friends even if you know they don't like the genre, maybe it could change their mind. You would be prepared to pay more than the average price in the media store.
10. ‘Perfect’
You could watch this movie/series until eternity without ever getting bored by it. With each viewing you discover something new or see something in a different light, and/or the key scenes still thrill you even though you know them by heart. This movie has nothing in it that is less than good. If there's anything that is not perfect, it is greatly compensated for by something else that is stunningly brilliant or gripping. You would recommend this movie/series to everyone, even total strangers. You would not be satisfied with a simple regular release when buying it, but you would seek out a special edition in a fancy box or wait for the ultimate director's cut and be willing to pay a premium price.