This was my favorite thread on the old r/OSR. So is your favorite system/systems?
I’ll start:
Basic Fantasy - BF gets overlooked a lot because the print books are sold at cost so I think it ends up being a lot of peoples introduction to OSR, but I keep coming back to it. The modules are really well written.
Old School Essentials - Just got the Rules Tome and I love it, though I haven’t had the change to dig into a game with it yet.
I am aware, I have Random Esoteric Creature Generator, been playing LotFP stuff since the original DFD, Grindhouse, & Green Devil Faces. But the problem is RECG helps you stock an exceptional monster or two. If you want a dungeon with many monsters, where the challenge is more strategic than “how do we stop the unstoppable armpit-licker from licking our armpits?”, you need a bestiary. And its game balance is different enough you do want stats customized to it.