I’m running two very slow campaigns in 3.5e and Greyhawk.
My email campaign started in 1998 in 1e, and we moved to 3e in 2001 and 3.5e when it came out ~2003? My players and I didn’t like 4e. Some like PF1, but we never saw a reason/consensus to change.
My family campaign (with in-laws and their kids in another state) was live during family get togethers, now 8-12 times a year on Zoom. I started 3.5e in around 2018, because I like it. My brother-in-law was the only one with D&D experience, going back to 1e, and also agrees 3.5e is the best version.
My version of 3.5e is Core rules (PHB, DMG, MM1-3 + FF, L&L, Living Greyhawk Gazeteer) with selected rules from outside that, like Feats players have wanted, ideas from PF1, and monsters from 1e I’ve converted.
Why I think it‘s the best is feels to me like the final, organized version of AD&D. 4e was too different and annoyed me as a player (my paladin’s sword attacks felt like spells), PF1 feels overpowered in some ways, and 5e I never played enough 5e to fully understand it.
I have a ton of 1e, 3e, and 3.5e materials - which BTW default to my favorite setting - and reasonable amounts of PF1, 5e, and Harn, with knowledge on how to convert all to 3.5e.