I really got into anime in 2018 with Little Witch Academia but as a kid my first anime ever was probably Nausicaa of the Valley of the Wind or another early Ghibli movie. Also as a kid I watched the Cardcaptor Sakura movies.
My first impressions were very positive. I was kinda primed to expect all anime to be trash and cringe so I was surprised when Little Witch Academia was actually just a great show. I've been watching non-stop since then, learned the language, translated some manga, etc.
My favorite series since I first watched it in 2020 has always been The Melancholy of Haruhi Suzumiya. Every arc is amazing, the characters are so interesting, and the presentation is so creative. Though I just recently started PaniPoni Dash! and it's the first thing that's ever challenged Haruhi for me; it might be my new #1. It's 2005 Shaft and it's kinda the peak of Shaft's style and quirkiness and it's also really funny.
I also just recently watched absolutely the worst anime I've ever seen: Kennel Tokorozawa. It is funny, which is a positive, but not enough to outweigh how overwhelmingly awful it is as a whole.
The worst things I've seen that (somehow) have an actual level of popularity and acclaim: Shinsekai yori, 86, The Boy and the Heron. All bad for different reasons, but each one irredeemably terrible.
You didn't ask, but I'll also mention what I think is the most underrated anime ever: Christmas in January. Amazing short movie. Not very popular or well-regarded, but very subtle and emotional and whimsical. Definitely the most "hidden gem" thing I've ever found.