For me the greener grass was right here in the US.
I came here from England five years ago. The reason was my American born wife wanted to return home, and though I had never thought of living outside England in a few months I found myself coming to the US.
Life is much nicer here. I do miss the seasons and English weather, but my taxes are much lower here, even gas at $4 a gallon is a lot cheaper than in England.
Here there is more space, if I want I can go to the mountains or enjoy the Pacific coast, I realize that would be difficult if I lived more inland, I can live in a much nicer house than I had in England and I find people in general much more friendly to me over here than was even the case in the town where I grew up.
So for me the grass is much greener in the US.