Depends on the game, but also the context.

Maybe this has changed since I’ve upgraded my gaming specs but I used to average 14 FPS on Kerbal Space Program and had a great time with it, docking is a nightmare at that frame rate but otherwise it’s more than playable.

Back in my poverty gaming days I 100%-ed a pirated The Simpsons Hit and Run with potato graphics at slide show speeds, I’m talking like multiple seconds per frame with around 80% frame droppage.

Nowadays I just care that it looks decent and runs smoothly for the games I play, which is mostly Civilization and Stellaris