24p running at 24p will look right, because that's how it's filmed. The exposure time is such that there is motion blur built into the image, and this "fools" us into thinking that the motion is smooth. This doesn't apply to stuff like computer games, where each frame is a perfect image (and motion blur is never any good in games) - this is why you need higher framerate in games to make it look as smooth.
When you start playing it back at a different rate, or doing a 3:2 pulldown, or creating frames, you interrupt that, and it always ends up looking worse.
When you start playing it back at a different rate, or doing a 3:2 pulldown, or creating frames, you interrupt that, and it always ends up looking worse.