I think the value of
Firefly lies in its categorization and technical aspects. For starters, you don't see many space westerns. Second, you don't see many sci-fi film and television productions that actively go against most of the typical trappings as space operas as much as
Firefly did.
From the characterization (flawed, relatively unheroic...generally realistic), to the universe (no aliens; Newtonian physics; interesting use of language, both in Chinese and specific English "slang" terms; technology isn't ultra high tech), to the filming techniques (unsteady, "zoomy" shots of the main characters' ship vs. sweeping, steady wide-angle vistas of the Alliance ships).... there's more than what I listed here. But what kept me tuned in and rewatching them was this nice departure from what I'd normally see or expect from sci-fi.
I also found it genuinely funny without it coming across as unserious (i.e. a comedy).
I'd like to see more of this kind of thing. Anyone who knows of anything else in this vein generally speaking, please let me know!