Well, Alcaraz is YE #1 but like the first time, he's gotten help. In 2022 it was Novak being banned from the AO and not getting Wimbledon points, and Rafa getting hurt. In 2025 it is Sinner's ban. Not saying it wasn't an impressive year--by my accounting it is around the 20th best of the Open Era, or thereabouts, but it would be nice to see him win it entirely on his own power.
Fun fact about Sinner's season: It is his second year in a row above 90% win percentage. It is only the 26th such season in the Open Era. Number of seasons with 90 W%:
5 Lendl
4 Connors, Borg, Federer
2 Nadal, Djokovic, Sinner
1 Vilas, McEnroe, Murray
Note absence of a bunch of ATGs: Laver, Agassi, Sampras, Wilander, Edberg, Becker, and Alcaraz. Alcaraz was really close, and assuming he has another couple seasons at least this good, he'll get there.
Fun fact: Rafa's two seasons with 90% aren't 2008 or 2010. They're 2013 and 2019. I still think that the best version of Rafa was 2013. He missed the AO and it was the Year of Darcis, but his overall level--especially through the US Open--was the highest of his career, imo.