aramis erak
Legend
Serenity was the first. Using Cortex Classic.The Unisystem Buffy game was great, some really innovative minor mechanics that really nailed the feel of the show. Just don't run your campaign too long because it breaks down when PCs have too many XP. Alien looks excellent, but i haven't played it.
The worst I've seen is possibly Firefly, which just had a dysfunctional system in many many ways. (The original version at least, apparently there was a much later revision that fixed the worst of it). D20 Star Wars was right up (down?) there too.
Firefly was the second game. Using Cortex Plus mechanics. I've found it to be excellent
Both from Margaret Wiess Productions.
There hasn't been a third.
At least not officially. Eden Studios Presents, I forget which issue gives a space western conversion for the Unisystem Light games (Buffy/Angel/Army of Darkness) to do Firefly, and it's a REALLY clear case of "We couldn't get the license, but are releasing it anyway" ... Giving a glimpse of what might have been had Eden gotten the license instead of Margaret Weiss Productions.
I agree Cortex Classic Serenity was a bit wonky. On the other hand, it's almost ratings compatible with the later Firefly game...
Firefly is one of my favorite hybrid games- rules to be used, leveraged, and not hidden, yet still easily fit to the story-state.
Having played FATE first, I see the kinship of Firefly to FATE, in both the nature of the the rules and the fit to the setting... but there just wasn't enough setting to really do it. At least, unlike early WEG Star Wars, the comics and novels weren't off limits. (But the Serenity movie was.)
10 great hours of TV, and 2 hours of a great movie... and two very different approaches to capturing its lightning in game form...