"points of view"

Points of view is the correct one. http://dictionary.cambridge.org/dictionary/british/point-of-view The rule of thumb is that the noun gets pluralized. The noun here is "point" and "of view" is the adjectival clause. example. "son-in-law" which becomes "sons-in-law"

"Points of view." See it as if the "view" were the source of your "points". Like "pieces of cake."

Three of them are correct. It depends on the meaning.