9/10: If not "perfect," it's perfect for me
8/10: Something flawed that touched me personally/A general consensus masterpiece that was basically flawless but didn't touch me personally
7/10: Watching it was entertaining most of the time, though I did have several issues/Watching it was boring most of the time, but the over all experience was still worth it in the end.
6/10: A positive "average." It didn't exactly bring anything new to the table, but I still enjoyed watching it
5/10: A negative "average." It neither impressed nor entertained me/something that I can't decide whether I like or hate
4/10: Bad in the sense of a recap episode--I feel something is boring or unnecessary, but it doesn't offend me personally. In the long run, it's forgettable.
3/10: It's a waste of my time, and I pretty much hate it all the way through. It may have one character or idea that I liked.
2/10: There's nothing for me here. Either I liked the beginning but hated it more and more with each episode or it was just plain bad with few (if any) redeeming qualities, such as animation quality
1/10: There's nothing for anyone here. Not only are there problems with the story and characters, there are also problems with the art, animation, voice acting, and/or soundtrack. An all-around horrible experience that I didn't enjoy at all.
Some people say that no anime should receive a 10/10 because no piece of media is "perfect." However, I believe that is something we should over look, seeing as if a 10/10 anime doesn't exist, neither should a 1/10 -- as long as the pictures move, it got something right. Therefore, I count an anime as "perfect" if it scores all 9s and 10s in the 5 categories used to review anime here on MAL. That, for me, merits a perfect score. I give 9s to shows that had a 10 in enjoyment but flaws elsewhere.