Spanish equivalent - the grass is always greener

Several.

"las manzanas siempre parecen mejores en el huerto del vecino" which is "The apples always look better in the neighbor's orchard"

Or ... "Gusta lo ajeno, más por ajeno que por bueno." One likes the "ajeno" (foreign, unattainable, distant), mor for being ajeno then bueno (good).

There's also "nadie esta contento con su suerte" or "nadie está contento con lo que tiene" which, while more literally translate to "nobody is content with his luck" or "nobody is happy with what he wants" are equivalent idioms.

Or, "Cada uno habla de la feria segun le va en ella" which is something like "everyone has his (her) own point of view."

--Amanda