What contrasting concepts of love are presented in Act I, Scene 1 of Romeo and Juliet?
There are a couple of concepts of love (and other things) that can be seen in this scene.
First, you have all the stuff that Sampson says. It's not love, really, that he's talking about, but it is relations between men and women. His vision of "love" is the sort of swaggering, bragging, women-are-sex-objects view of "love."
Then you have Romeo's "love" for Rosaline. His is a sort of pathetic infatuation. He idolizes her and plaes her on a pedestal. His "love" for her makes him weak because she won't return that love.
So the contrast is between two things that I wouldn't even call love -- there's treating women as sex objects and treating them as unattainable and perfect.