The Grass is Greener On the Other Side of the Fence
= always the things other people have or their situations always look better than your own
Ex. In America, the Beatles have the most #1 songs. While in England, Elvis has the most #1 songs. I guess, “the grass is greener on the other side of the fence.”
Ex: Teenagers always think their friends have better lives. They always think “the grass is greener on the other side of the fence.”