Looks like that's where the Combine is going to put the new Citadel...

Excellent point, and one that I have made repeatedly when this topic comes up. We haven't heard anything yet, because we are the first to emerge, at least in our region of space. The universe is 14B years old, and our solar system is something like 4B years old. Our system could only have formed after at least one prior generation of hotter, simpler stars went nova and seeded the ubiquitous hydrogen and helium clouds with heavier elements. More likely, it took 2 rounds to make sufficient quantities and allow them to cool down into stable bodies. And that doesn't even mention some of the remarkable circumstances around our particular planet that created a stable environment. The planetary impact that split earth open and created the moon also let huge quantities of molten iron sink to the core, forming a spinning magnetic shield that guards against radiation. The moon itself stabilized our orbit and throws off other bodies that might collide. Jupiter has done much to sweep the inner solar system of debris. It's certainly likely that there are other planets like ours out there somewhere. But this combination of lucky events and relatively early planetary stability is probably rare.

Call it the blurker hypothesis. Think about it. The universe is maybe 14b years old. Our own planet is about 4b years old. For Earth to form, there had to be a giant dust cloud full of iron and other heavy elements, which can only have come from novae/supernovae. So at least one generation of stars had to form, burn out, explode, cool to ash, and then reform into new gravity wells to form this solar system. Since this one is about 4b years old, and can be expected to make it another 4b or so, then that leaves a tidy 10b years for a previous star cloud to seed our local region of space. Seems like just enough time. So we haven't seen other intelligent life yet because we are among the first ones to emerge from the ash...

Can't we get a whatcouldpossiblygowrong tag on this post? Please?

I for one WELCOME BACK our Rock and Roll OVERLORDS!!!