I make videos comparing scenes from 2 movies. I use scenes (it's always more than one movie) or scene in the title?
You should probably use "scene comparisons" in the title. It is partially due to the fact that generally though we compare a multitude of things, at a time we're looking at one specific scene in, say, movie A with a similar/contrasting scene in movie B.
It has a resemblance with "profit comparisons". Although the profits are of more than one type (net profit, gross profit, operating profit, etc.), the singular form "profit" is more commonly used.