Ashen Stars
The dream of the bounty hunters roaming the galaxy in the search of adventures, money and survival can come true with this game. It is based on the tested-and-true Gumshoe System that offers uncanny possibilities to be immerse in a huge world for the longest hours. Mystery Sci-Fi in the deep space on board of a ship, facing dynamic and changing challenges is what this game can offer. Start your engines, set course for the deep space and let this awesome game surprise you.
Paranoia
This might be the best game for those who really want to spend just one afternoon playing with friends and not make a long-term commitment. The world-creation engine is very focused, so you won´t be going over your head with it creating huge scenarios. What really sets this game apart is the use of black humor. It offers the ability to double-cross or backstab your buddies and perform all kinds of dishonest moves which is utterly funny most of the times. The spirit of the game is fun and makes for a great afternoon of snacks, friends, beers and laughter.
Traveller
This game must have the most complex structure I have ever seen in a tabletop RPG in my entire life. The dense rules book contains such detail that makes the beginning of the game very intricate. Once you go beyond that moment (which was quite hard) and master the rulebook you can go as far as creating your own planet! There are gravitational, government, atmospheric composition and climate details that can be added. By the middle of the game, you might even have your own half-galaxy setting. This might be the densest game you´ll ever play but also the most rewarding.
Cyberpunk 2020
Perhaps not so well-known as most of the ones in this list, but I have a spare portion of my heart for cyberpunk settings. This game is based on a free version of the classic novels by authors like William Gibson and as you might notice from the name it is… two years from now? Well, nostalgia gets me from time to time and also the character creation, game rules and combats are awesome. There is a lot of retro-futuristic action waiting for you.
Special Mention: Star Wars
While it is true that Star Wars involves space travelling and alien beings, it is also true that the opening says “a long time ago in a galaxy far, far away”. So, technically it is not a futuristic RPG.
As much as I love using my imagination freely, every tabletop RPG game I´ve played has been a great experience.