God, I've been down this rabbit hole more times than I care to admit. You'd think there'd be a central hub, but honestly? The best recs I've found come from places you have to dig for, not the obvious ones.
A site like r/nhentai on Reddit is a good starting point, but the real gold is in the comments of specific doujin pages on the site itself. If I find an artist or a tag I'm really into, I scroll through the comment section there. It's a bunch of degenerates just like me, leaving recommendations for similar stuff right under the thing you just read. It feels more organic than a curated list.
I've also had surprising luck on really niche Discord servers dedicated to specific kinks or art styles. You have to wade through a lot of... everything... to find them, but once you're in, people share codes and titles you'd never stumble across on your own. The main thing is knowing what you're looking for – 'best' is so subjective. Are you after a specific dynamic, or just trying to find something that hits as hard as that one story you can't remember the number for?
My personal method is bookmarking artists I like on nhentai and checking their 'related' tab, then letting the site's own algorithm take me down a weird, wonderful path.