Where have all the aliens gone?

Are we alone?

General cases of race development, extinction, good versus evil
Where races evolve to transcend the visible universe
Holistic approach to advancement (good-evil neutrality, Godhood, enlightenment)
Human race - either we are the first, first of many disconnected at similar tech or universe is turned by hyper-evolved beings (us in a previous iteration).

Universe as the inside of a great but highly logical mind - possibly a collective machine consciousness. Humans as experience or needed factor to be able to think or cope with illogical and emotional paradigms.