I have watched anime since I was 12 years old. I have been fortunate enough to grow up at the same time as some characters did, for example, Harry Potter and Naruto. My ratings are all over the place since my taste in anime has evolved and matured over time. I'm definitely more careful now at giving away high scores to anime than I was at the start of my journey. So take my ratings with a grain of salt.
I watched many bad and mediocre animes when I was younger, I used to watch maybe 10 per season. Although Ergo Proxy was one of the first Animes I watched. So it's not easy to guess either how old I was when I gave my ratings to certain series that you might not agree with. Today I'm super picky about what I watch and only watch 1 or 2 animes per season together with One Piece.
I've given up on trying to fix my ratings, they are what they are, I'm not a professional reviewer nor do I strive to be. What I can tell you though is that the 10's I have given out are legit. You may not agree with them but I stand by those ratings today and I can explain why I gave them a 10.
For me an Anime that recieves a 10 from me might not be a perfect anime because there are no perfect animes in my opinion. There will always be something that could have been better. Does that mean we should not use the 10 rating? I don't think so. A 10 for me is an anime I absolutely love. It's an anime I remember very well and can rewatch and have rewatched one or more times. There can also be sentimental value, one of those would be Naruto Shippuuden. Like I said I grew up with Naruto, growing up and following that story to the end was truly epic for me. I loved the drama, the gruesomeness and music. It's something I will never forget. With that said, I can totally see and predict that it probably would not get a 10 for me should I have watched it recently.
Another one of the first Animes I ever watched that wish I could give a 10 is Claymore, that was my first heartbreak and the first time I ever cried watching an anime. I have probably rewatched it more than 3 times. There is so much nostalgia for it. I love the gruesomeness, drama, battles and music. The alternate ending and unfinished story for the anime is a real shame. That's why I couldn't give it a 10. I'm hopeful for a remake.
Another 10 is One Piece, I absolutely love that anime. There is a similar nostalgia to Naruto but it's just better and I'm astonished at the creativity and endurance of Oda Eiichiro, that after 900+ episodes it still has so much to give. In my opinion One Piece is probably the best Anime logically for this reason. A good idea might be to think about the whole list 1 rating less, with One Piece and perhaps a few other ones staying at 10. If there is an anime that's rated 8 for example and it's too high in your opinion, it's probably a 7 with a few exceptions.
Great Teacher Onizuka. The funniest Anime hands down. After the 5th rewatch it still makes me laugh.
Nodame Cantabile. I just love these kind of stories like Bakuman and Uchuu Kyoudai where the characters work hard and become successful doing something they love with a slice of romance and comedy. There are many like it but I felt these 3 were the best. Nodame Cantabile made me enjoy classical music. It Introduced me to Rachmaninoff and that was just the start where I actually started to listen to classical music and ended up going to concerts. My favorite music is still Metal though.