Movies are 24 fps, I'm pretty sure about that. Some Saturday morning cartoons can run as low as 4-6 fps, depending on how cheaply they are made. Some older ones (like Looney Tunes) are probably much higher fps because originally they were created to run in movie theaters before the main attraction.

As for the rate at which your game will look best, I think the most important factor is the consistency of the frame rates, once you are over ~20 fps. If your game was rendered at a consistent and steady 24 fps, it would look very smooth to the eye, possibly just as smooth as 30 fps or even 60 fps. If you are getting 60 fps but every now and then you get a drop to 40/50 fps, I think your eye registers the changes and you notice the flicker or stutter.

None of that is scientific by the way, so I may be wrong. :P