Telika: Generally hate fanfic, have no interest in reading or watching any. For me, it's a purely derogative term.
I understand that they must be immensely fun to make, though, like playing pretend you're the last hero you watched or read about, or daydreaming about some universe you've enjoyed. My first homemade comics, as a kid, were tintin fanfictions (and that was before I knew how to write : I had grown-ups filling the captions on my instructions). Making fanfiction is certainly an entertaining activity.
I just think that 1) it's a clumsy, amateurish, sub-par, version of the original material. 2) it's a cheap creative activity, sparing the trouble of building up one's own universe, style, characters.
So, exceptions. Nuka-break is impressive. The fan comics with all the Doctors was quite nice too. Parodies are fun, although the limit between parody and fanfic is sometimes unclear. And the high drama when fanboys clash around some blasphematory fanfic is adorable (saw an "alien vs predator" forum go nicely down in flames after a student writer wrote an homosexual love story between Hicks and Hudson). Plus, real real bad fanfiction is hilarious.
I couldn't say which is worse. Game characters are generally less fleshed-out than cinema/litterature characters, so there is less to betray : games are more directly about putting yourself into some characters and "bastardizing" them. In a way, every play run is already some sort of fanfiction (FTL travels accounts, for instance). Actual fanfiction is going eyond in-game events, but in a way we all complete in-game events with some amount of roleplaying. Heck, even in chess (with our "courageous little knight" and "oooh no that heroic pawn went soo far but got let down by the selfish bishop he relied on"). I'd say that cimema/book fanfictions hijack (and unwillingly clumsily betray) more.
Also I treat most by-products as mere fanfictions already (official star wars novels, post-fleming james bond books, etc), with some varied level of forgiveness. Again, Troopers was immensely awesome. But because it clearly departed from the original work's angle and tone, and wasn't just a "ME TOO!" prologation.
Will edit for links.
I would have thought so too but this is only a pre-conceived notion since the poignancy of fan fiction to a great degree levies upon the skill of the writer. So while you may some fanfics that are utter tripe there may be a few that are truly exceptional.
For the record the anime gun grave was actually based on a video game with little in the way of a plot but it turned out to be one of the most trenchant animes that I have ever seen reminiscent of the god father meets erm dead heat?
