MyAnimeList has a composite metric of popularity of anime, which includes the total sum of all people who have listed an anime as any of Watching, Completed, On-Hold, Dropped, or Plan to Watch on the site.
This market will resolve to the seasonal TV anime (listed as new in any of Winter 2024, Spring 2024, Summer 2024, or Fall 2024) that has the most people who have listed the anime on MyAnimeList at the end of the year, Japan time.
For reference, the top anime from 2023 are (numbers at the time of market creation):
Jujutsu Kaisen 2nd Season: 853k
Kimetsu no Yaiba Swordsmith Village Arc: 780k
Oshi no Ko: 753k
Jigokuraku: 646k
Vinland Saga Season 2: 578k
Sousou no Frieren: 558k
For 2022 anime, the top anime are (numbers at the time of market creation):
Chainsaw Man (1.5M)
Spy X Family (1.5M)
Kimetsu no Yaiba Yuukaku-hen (1.4M)
Shingeki no Kyojin Final Season Part 2 (1.3M)
Sono Bisque Doll (1.0M).
This question will not take into any TV anime that is continuing on from previous years. It will also not take into account any Movies, OVAs, or Specials.