Chris Conselice, University of Nottingham, says there could be 36 intelligent races in our galaxy (the Milky Way) using a data-based technique called the Astrobiological Copernican Limit. There are of course a hundred billion galaxies (possibly two hundred billion) so it should be teeming with intelligent life out there.
The average distance from us within our galaxy is 17,000 light years (so eighteen of those life forms will be closer, don't forget). With our current technology, it would take millions of years probably to encounter the nearest intelligent life form. Of course, other older civilisations out there might be more technologically advanced and may have already found ways to manipulate space-time or other dimensions to move more quickly - or at least to send data.
Look at how much we've achieved in the last 100 years - imagine if the other life form was a million years in advance of us? (Maybe, they are already here in the form of shape-shifting aliens and they walk amongst us? Urrghhh - creepy)
Leaving all that to one side, here's the important bit:
Now we are pretty sure they exist, maybe comic books have correctly predicted them - as they have so many other things, so - Who are your favourite golden age alien races - let's say from 1935-63 - and why?