By Earth cameos, I mean games that are definitely NOT set on earth mentioning the pale blue dot. Sci-fi games set in deep space that talk about the human homeworld or games with hidden (or not so hidden) post-apocalyptic settings would both count.
I'll start with an example that's not one of the usual suspects. In Dungeon Fighter Online's lore, Earth was blown up a long time ago and New York City started floating through space. Eventually it became known as Pandemonium, a place where absurdly powerful magical beings hang out and beat the shit out of each other. So powerful, in fact, that for the longest time it was only featured in lore and it was only after a whole decade of MMO power creep that players could actually visit Pandemonium.