I make no bones about the fact that, when it comes to science fiction RPGs, I was and remain a Traveller man. Traveller was, after Gamma World, my first SF RPG, and the one I undoubtedly played the most. My first professional writing credits were for Traveller and the first game industry professionals I ever met in the flesh were associated with the game (at the 1991 Origins convention in Baltimore, where I had dinner with Marc Miller, Charles Gannon, and the Japanese translators of Traveller). To this day, when I think of "science fiction roleplaying games," Traveller is the gold standard by which I measure all others.
Though first, Traveller wasn't the only SF RPG out there. In 1980, Fantasy Games Unlimited released its own entry into the genre, Space Opera. Rarely has a RPG gotten a title so evocative and apropos, for, unlike Traveller, Space Opera was unambiguously -- and clearly unashamedly -- an "unserious" game. By that, I don't mean it was a jokey or silly game, only that it had no pretensions to being a "deep" game, ripping off, as it did, just about every bit of SF its writers could get their hands on. As you can see from the cover image, this is a game where Flash Gordon, Chewbacca, Ming the Merciless, Barbarella, and assorted aliens can meet in a cantina and go adventuring among the stars without the petty concerns of rhyme or reason. In concept, it's about as coherent as Dungeons & Dragons but, like D&D, it has the potential to transcend its schlocky origins and become its own weirdly appealing thing.
Alas, Space Opera never could reach such heights of gaming enjoyment because its rules were terrible, possibly unplayable. Though written during what I call the Golden Age of Gaming, Space Opera nevertheless evinces a Silver Age obsession with complexity and I dare say "realism." Character generation is a long and tedious process, involving a combination of random rolls, derived attributes, and player choice. Unlike Traveller, where even a fairly experienced character can be generated quickly, doing the same in Space Opera could easily take 30 minutes or more, especially if you're not very familiar with the system. Combat involved multiple rolls for each attack: to hit, to determine where one hits, to penetrate armor, and to determine extent of injuries. Space combat was even more complex -- as were most of the game's systems.
Now, as you should know by now, I don't see anything wrong with multiple sub-systems within a game. Indeed, I am increasingly convinced that one of the hallmarks of old school design, as opposed to nostalgia games, is that they are built upon multiple, separate sub-system that work in unison rather than a single universal mechanic. Space Opera falls down, I think, because its various sub-systems don't work in unison. Instead, they give the impression of a Frankenstein's monster, sewed together from bits and bits pieces scavenged from here and there without any regard for what the end result would be. A friend of mine, who's played more Space Opera than I ever could stomach, suggested that the game was written by a committee of people who were each given a separate section of the game to write and who didn't like each other very much. As it turns out, he's almost right. According to FGU's Scott Bizar, Space Opera was written by correspondence by several authors who'd never met one another; it shows.
Nevertheless, Space Opera had a slew of supplements between its initial release and 1985. Of these, the Space Atlases are the most interesting, for it's here that you get a sense of the glorious cheesiness of the game's official setting, which I can only describe as "kitchen sink SF." You remember those guys in high school who used to argue about whether the Enterprise could defeat an Imperial Star Destroyer? They went on to write the Space Atlases, where the United Federation of Planets -- yes, they call it that -- can fight Space Nazis, Space Soviets, and the Space Viet Cong/Mongols, not to mention the Bugs from Starship Troopers. There are Vulcans and Kzinti too, along with many other ideas torn bleeding from the bodies of science fiction books, movies, and TV shows.
To be fair, Traveller's official setting is also highly derivative, swiping heaping helpings of ideas and terms from H. Beam Piper, Poul Anderson, Larry Niven, and Jerry Pournelle, among others. But Traveller somehow managed to hide its sources better and its rules were simple enough that you could very quickly get into enjoying the game itself so that its derivativeness faded in importance. Space Opera never managed to achieve that degree of unity, largely because its rules are such a mess. I think that's a shame, because a gleefully schlocky SF RPG is a wondrous thing to play.