Selfish, Quiet Girl
What animes have you watched that you would call masterpieces?
Let me just say i’m not sure if any anime can truly be considered a masterpiece sense as we grow older our interests and views change but if your talking about anime that should be remembered then i can show you my recommendations.
When it comes down to what's considered a “masterpiece” it's usually in the eye of the beholder and it all depends on what genres your interested in.
As for Slice of Life i’d say K-on wins by a landslide for me but i’d also highly recommend Three leaves Three colors
For Comedy it's hard for me to say there's any thats fully fantastic but i’d recommend Gamers! or Squid Girl
Action isn’t my strong suit or anything but it depends on what you're looking for, if you want superheroes type action in current time I’d say My Hero Academia is a good choice.
Or Soul Eater For Fantasy Either Magi, or HunterXHunter 2011 For Romantic or RomCom I’d say My Love Story or Fruits Basket For Horror there's not many that i hugely enjoyed but Another was interesting If your into Mecha i’m not a huge fan of it but Full Metal Panic is good If your into high amounts of fanservice might i suggest Heaven's Lost Property or Kanokon If a harem like anime is what you would like I would recommended my personal favorite The World God Only Knows (seasons 1 & 2.
3 screwed the series IMO) and Haganai When it comes to Supernatural anime perhaps either Blue Exorcist or Ghost Hunt In terms of Military Anime of which is my Favorite type of anime I highly recommend Youki Senki (or the incorrect english name Saga of Tanya the Evil) or Alderamin on the Sky For Isakki Titles (or to another world anime) of which i also enjoy quite a bit I’d recommend No Game No Life and Gate I’m not huge into food anime but if you enjoy stuff like it i can only recommend Restaurant to another World For drama i’d say ef: A tale of melodies and Puella Magi Madoka Magica For psychological anime i’d say Welcome to the NHK and Psycho Pass season 1 I don’t like most sports anime but sense the show considers this a sport i’m gonna say Chihayafuru In the end it all depends on what you like at the end of the day.