When we look at tabletop RPGs, we see that fantasy is the most popular. Nearly everyone plays a fantasy RPG. Even famous science fiction games like Shadowrun aren't really that widespread. Plus, it's mostly a fantasy game anyway.
Why are science fiction RPGs less popular? It's not the genre itself - science fiction computer games, movies, and comics are at least as popular as fantasy.
I've thought about it, and I've come up with two big problems with science fiction tabletop games.
The first is that they aren't as easy to imagine. Science fiction games tend to have bigger, stranger things to think about. That means that the player has a harder time imagining them. It's easy to imagine a swordfight, trekking through a bog, sneaking through the dark, or looking out over a mountain range. At the very least, we've played at those things in real life. But it's much harder to imagine rescuing a stranded astronaut or saving the day with a piece of clever code.
These bigger, stranger images are the ones I prefer, and I think a lot of people feel the same way. Although most science fiction fare these days is basically action flick crap with a science fiction gloss, it still has big, powerful imagery. In computer games and movies, it's easy to show these images. An AI flickers into existence. A plague mutates the local wildlife. A gleeful coder hacks a mainframe while surrounded by massive screens. Biological cells bond to plastic, and your eyes reboot into Terminator-vision...
But when you look at a scrap of paper with words on it, those things are hard to portray. If I see a picture of a sword, I can immediately understand everything and imagine going to battle with or against the sword. If I see heavy armor has a speed penalty, I can immediately imagine a slow, armored knight against a fast, unarmored rogue. If I see a castle, I can imagine a siege. Etc.
If I see a robot... the images don't pop into my head nearly as fast. The robot looks cool, but there's no "AND THEN" going on. I don't automatically think about the scenarios the robot would be part of. Same with space ships, cybernetic enhancements, life support systems, computers...
Now, the first thought that popped into my head is that you simply need to be a lot more aggressive. When you describe a robot, lay out a fragment of a scene to give the player something to grip onto. When you describe cybernetics, have an NPC talk about something that happened to them because of the cyberware.
If it's hard to imagine, give the player a leg up. Easy enough!
But... this brings us to the second big problem with tabletop science fiction games.
Fantasy games can be thought of as running around in the back yard waving a stick around. Science fiction games can be thought of as running around the house with an armful of plastic toys making "whoosh" noises. As soon as you succeed in landing a plastic rocket on the couch and your action figure gets out to explore the surface of this alien world, you'll understand the appeal of science fiction.
That is, fantasy games are about your personal merits. Your strength. Your cunning. Your speed and willpower. You may use all sorts of equipment, but in the end it's about proving your mettle.
Science fiction games are mostly about STUFF.
Your space ship, your antigravity belt, your supercomputer, your robot arms. And of course, all the other stuff: that nebula, this space station, that mind-control laser, this ancient databank...
"Wait! Fantasy games have tons of STUFF in them!"
Definitely. But science fiction is fundamentally about how people behave when situations are different. The STUFF in these settings defines how people behave, what questions are being asked, and so on.
That said, it's definitely true that there is a vast amount of STUFF in a fantasy game. Massive amounts of stuff. In fact, most fantasy games have more stuff in them than most science fiction games!
Even the giant stack of guns in Shadowrun doesn't hold a candle to the array of weapons in D&D. And it's not just a matter of how old and widespread the systems are: D&D is fundamentally more stuff-heavy because it lets you arbitrarily augment or craft your own stuff. Enchanted swords, special potions, new spells, armors made of rare new materials. D&D has a literally infinite variety of swords. No matter how many different guns with different ammo types Shadowrun lists, they simply cannot keep up with that!
Hm. What the hell do I mean that science fiction is about "stuff", then?
Well, look, fantasy games are about personal merit. But there's not a lot of personal merits in them. There's a few stats, an alignment, maybe some personality traits, and a class. These things determine your personal merits. They determine who you are.
In turn, these merits serve as an anchor. The game has a vast statistical maelstrom of STUFF. This is the meat of the game, where all the players struggle and fight. The merits you have serve to anchor you within this maelstrom, so you can participate without getting swept away in confusion. You're a mage with a high speed? This is where you stand. A warrior with low charisma? This is where you stand. Your personal merits mean you'll approach the situation like such.
Most science fiction tabletops take this same approach. But that misunderstands a lot.
Because fantasy games are about your personal merits, they feature things which are easy to personally imagine. Even a dragon or a giant dwarven hold is something an individual can imagine pretty easily. They can hold their merits up against these challenges and see what kind of struggle would happen, what kind of standing they have. The vast array of statistical gear and spells and such allow them to grapple with these figments, pushing and pulling at the things they can do... but the things they can do are still rooted in their perception of who they are, their personal merits and traits.
Science fiction tabletops try to hold that same line, but the setting of a science fiction game is about STUFF. So you're a hacker, a smuggler, or a space princess - you have all these traits... but the setting is about a planet that's being colonized, or an ancient civilization, or a disease, or a robot rebellion. These are not things affected by your personal merits.
A smuggler or hacker can certainly get involved with all these scenarios, but the scenario is both larger and more lively than they are. A hero could imagine fighting a dragon... but a hero is of a lot less use when a radiation storm is inbound. A hero can imagine walking the ten thousand steps of fire... but those ten thousand steps are just a barrier to overcome, not a living thing like a space station full of refugees.
In the end, the setting sabotages the game. The game is built around individual merits, but the setting doesn't give a shit about your individual merits. The setting cares about STUFF.
Well, stuff isn't bad.
See, fantasy games can build this giant maelstrom of stuff on top of a setting that cares about personal merits. Science fiction cares about stuff, so it may be possible for us to build a giant maelstrom of personal merits.
This is really what science fiction is about. It's about a foundation of specific assumptions, and seeing how that affects the people. "What if space ships could travel faster than light?" "What if we were psychic?" "What would people do if aliens invaded?" "What happens when robots can do our jobs better than we can?" "What if our TVs were able to watch us?"
The STUFF here is very specific and limited. Robots that can do a specific kind of thing. A government that acts a particular way. A space ship that can move a specific way. There's not 10,000,000 different kinds of robots, each with their own stats - it's just a few kinds of robots to set the stage properly.
And from that foundation blooms an outpouring of human behavior. How do people behave? What do they do? How do they feel?
This is where the powerful imagery in science fiction tends to come from.
The images Roy Batty describes - "Attack ships on fire off the shoulder of Orion... c-beams glitter in the dark near the Tannhäuser Gate" - these are not things with any clear image, but they can still make you shiver. They are mysteries to us - but Roy has been there. He's been there, and he remembers, and he's fighting to live.
Roy's life is defined by the stuff he's seen. Roy's struggle is defined by the stuff he's seen. Roy is defined by the stuff he's seen.
By stamping down a foundation of stuff, we can allow people to shine, both as individuals and as groups.
So why don't any science fiction games work like that?
Well, because nobody's written one yet.
I can't pretend to have a good set of mechanics in mind. I'm still thinking this through. But logically, a few things seem clear.
First, the stuff is less complex and the personal merits/beliefs are a lot more complex.
Second is that you would choose your stuff more carefully than your personal characteristics. You don't need to know if you have a strength of 14. You need to know that you have an antigravity belt or Jedi powers. Those will provide a foundation for interacting with the challenges in the game. The personal merits like strength can vary over time or be completely unimportant.
Third is that your personal merits/beliefs would not be concrete. For example, in a fantasy game you'd choose "self-confident" as a trait and it'd stay forever. In this game, the self-confidence comes in many forms. There are times when you'll lose confidence, times when you'll only have confidence in certain ways, and times where your confidence doesn't matter at all. Just like wielding a sword in a fantasy game: you can drop it, replace it, and sometimes you'll leave it sheathed.
Fourth is that combat cannot be the focus. Combat is fundamentally about personal merits, so it can't be the foundation mechanic. The foundation mechanic needs to be about stuff. You won't struggle to kill goblins: you'll struggle to push through a mind-control laser beam. You'll struggle to get robots accepted as people. You'll struggle to keep death at bay.
I hope I've been clear. Let me know if you understood what I was trying to say.