These "10 of the best" lists are lists exploring sci-fi sub-genres.
From Wikipedia: "Space opera is a subgenre of science fiction that emphasizes space warfare, with use of melodramatic, risk-taking space adventures, relationships, and chivalric romance. Set mainly or entirely in outer space, it features technological and social advancements (or lack thereof) in faster-than-light travel, futuristic weapons, and sophisticated technology, on a backdrop of galactic empires and interstellar wars with fictional aliens, often in fictional galaxies. The term has no relation to opera music, but is instead a play on the terms "soap opera", a melodramatic television series, and "horse opera", which was coined during the 1930s to indicate a clichéd and formulaic Western film."
