I can't really choose the Star Wars or Star Trek movies as so many of them are rubbish. I think this question is asking me for a film series mostly set in space and I can only think of one other. I wish there was a Serenity series to pick but sadly that seems unlikely to happen. So that leaves me with the body-horror bad guys. With Colonial Marines who, if you were paying attentions, got their asses kicked. With shaven headed prisoners and a dog/bull beastie. And finally with the strange mix of Joss Whedon, the director of Amelie, and Ron Perlman.
I really like the Alien movies and I'm looking forward to the forthcoming Prometheus. Those creepy Giger monsters are my favourite space series.