I think 'The Martian' was extremely popular. It was widely praised for its scientific accuracy and the engaging performance of Matt Damon. People were really drawn to the idea of a man alone on Mars trying to find a way back home.
Probably 'Star Wars'. It has a huge fan base all over the world. The epic space battles, the Force, and the diverse characters are really appealing.
One of the great science fiction works in 2018 could be 'The Calculating Stars' by Mary Robinette Kowal. It combines an alternate history with the concept of space exploration in a very engaging way.
One of the popular 1889 science fiction works was probably influential in its own right. It might have introduced unique concepts or settings that hadn't been seen before.
One popular 1899 science fiction work was 'A Trip to the Moon' which was significant as it was one of the early forays into the idea of lunar exploration in science fiction. It captured the public's imagination about the possibility of traveling to the moon.
One great ace science fiction is 'Dune' by Frank Herbert. It has a complex and detailed universe with unique political, ecological and religious elements. Another is '1984' by George Orwell. Although it was written as a dystopian novel, it has strong science - fiction elements, like the omnipresent surveillance state. Also, 'Brave New World' by Aldous Huxley is a classic. It presents a future society where people are genetically engineered and conditioned from birth.
Another great one is 'Star Trek'. It has created a vast universe with different species and technologies. It often explores moral and ethical issues in a science - fiction setting. For example, the idea of exploring new worlds while respecting other cultures.
Some of the popular ones might include 'Dune' related discussions. 'Dune' has a complex world with its unique politics, ecology, and characters, which often sparks in - depth conversations on Stack Exchange Science Fiction.
I'm not sure which ones are the most popular exactly, but 'Snow Crash' by Neal Stephenson is often highly regarded. It's set in a future where the world has been transformed by a new form of technology and virtual reality, and it has a really unique and engaging plot.
Another popular one might be 'The Uplift War' by David Brin. It's part of a series and in 1989 it was attracting a lot of attention for its unique take on the evolution of intelligent species and the politics between them.
I'm not entirely sure which ones were the most popular, but 'Doomsday Book' was widely talked about. It had an interesting premise of time - traveling historians.