So this is a discussion I've been having with my girlfriend the last few days. We've been focusing more on the negative side (basically, what's the most frightening/dangerous scifi universe) but there's an interesting argument to be had the other way as well. 

What I think makes this such a hard choice is that most of the major universes have their selling points but also have some pretty big (read: horrifying) drawbacks. 

To wit: 

Mass Effect: Space magic, plus lots of cool alien species who more or less peacefully coexist with each other, but also there are ancient AIs who wipe out all intelligent life every 50,000 years.

Star Trek: If you live in the Federation, you can look forward to a utopian, free, high tech society where things like poverty, racism, even scarcity (and with it things like the need for currency) have been made a thing of the past BUT there's also the Borg who could literally assimilate you and the rest of your planet at any moment. 

Star Wars: A vast Galaxy of diverse cultures and experiences, cool ships, space magic (again), but also at any given time more than half the Galaxy is either run by tyrannical dictatorships or completely lawless.

So what do you all think? What would your choices be and why?