I'm 26 years old. I started watching anime (excluding pokemon and yugioh because I hardly consider those anime, more like cartoons) in late middle school early high school? on Adult Swim. My first animes were Inuyasha, Wolfs Rain, and Witch Hunter Robin. I didn't watch much beyond that until I was in college and figured out how to watch online (yes I know it's not that difficult) and then I spent years watching anime every day. Though, recently I watch very little.
Some of my favorite animes are: Mirai Nikki TV, Rainbow: Nisha Rokubou no Shichinin, Inuyasha, Code Geass, Attack on Titan, Arslan Senki (2015), Junjou Romantica, No. 6, Steins Gate, Another, Angel Beats, Jormungand, Black Butler, and more.
My least favorites that I have actually fully watched (or close to) are: Shakugan No Shana Season 3, Chaos;Head, Death Parade, Baka to Test to Shoukanjuu, D-Fragments, SOA.
Favorite Movie: Kiki's Delivery Service (No matter how old I get or my tastes change, I like this movie)
I write reviews when I have time although due to time and a bad wrist I keep a lot of them short.
What makes an anime good in my opinion is not much different from what makes a good story period. It has to have a beginning, a middle, and an end. The beginning should draw me in. If you lose me in the beginning, what's the point of even having anymore episodes. The end should be conclusive. It should tie up that part of the story. It should provide closure. It doesn't have to reveal everything, especially if there is already a second season planned, but it should be conclusive enough that it can stand on it's own if it has too. I shouldn't have a billion questions. A conflict should have been solved and it should be the main conflict of that season. The story needs to be developed well too. The plot should have the proper structure and be well paced. The characters should also be well developed and interesting. Sterotypical characters need less development but should still be interesting. Depending on the genre, not all of these things will apply equally, however, the ending is the most important thing to me in the end (lol...okay bad joke I know). I don't care how good the rest of the anime is, if it doesn't have a good ending that concludes the story, it might as well not even exist in my mind.
Animation style and art style matter somewhat. There are some styles that are beyond my ability to tolerate regardless of how interesting the story seems. As long as it's pretty normal though, I don't care about it much. It's the same with sound.
There are other things that apply only to certain genres, but I won't list them.
If you don't like my reviews, write your own.