I was just reading Psalm 37 awhile ago, and reading those verses in context really helps to demonstrate why this is a case of proof texting. The term 'earth' could just as easily be rendered 'land', which for the Jews was the main hope--to possess their land 'to time indefinite', which was clearly an oft-used expression of those times ('O king, live on to time indefinite' was hardly expressing a hope that the king being addressed would live forever on a paradise earth, after all). Righteous, meek people would hope to pass on their possession of land to their children, and their children, and so on, in ancient Israel. This song could easily be interpreted as an encouragement to live honorably in contrast to the wicked who would suffer the bad consequences of breaking the Law (ie. being killed and their land being handed off to someone else, maybe even someone not of their household or blood line).
I'm not saying that there can't be a paradise earth; I'm just saying that Psalm 37 does not necessarily prove that. I've seen enough word replacement in the New World Translation to safely conclude that the use of the term 'earth' could be an intentional propping up of their doctrines about paradise. That's my take on it.