I played early 3d games with framerates in single digits, and some probably dropped way below 1 fps (meaning it took 2 or 3 seconds to draw a frame).
They were still playable, because they were designed with that in mind.
Don't make me maneuver through fast bullet hells at 20 fps and there's no need for my point and click adventure to be 120fps.
I'm no framerate elitist for the sake of it, I'm ok with any framerate doesn't get in the way of playing the game, which entirely depends on the genre and pace of the game itself.
Some will say that anything below 30 (heck, even 60) can't be tolerated but in the end everyone's "omg best game ever !!11" was a 15 fps affair.
Similarly, drops are generally acceptable when they don't get in the way, or not too often anyway