I also watched Serenity first and then the series but I still like Serenity.
The only thing I didn't like about the movie after watching the series was Wash dieing. Sure it was a pointless death done solely for the sake of having someone die (the Agent from the Avengers suffered the same injustice imo) but after getting to know and love the character with the series that pointless death stung.
Then again I haven't seen either show and movie in ages so maybe my opinion would change if I watched them again.
SGA was just simply rushed, there's nothing else too it. They were told at the 11th hour that there won't be any more SGA so they had to quickly throw something together as some sort of conclusion. Though there's probably something deeper to this as SGA was
sacrificed for SGU, possibly from the request of SGA's creators I heard once.
This is kind of why I don't bother with TV shows anymore, why get invested in a story and its characters if everything is just gonna stop halfway through for no good reason? That and there's not generally anything worth
watching these days anyway.
I think in part it's also the creators fault for making series with a continuing story from season to season. Maybe if more shows were like Dexter* where each season has its own self contained story this wouldn't be a problem because then a random cancellation won't mean a current storyline won't be left unfinished.
*At least Season 1-3 were. Season 4 ended in a cliffhanger and I never watched anything past that.
The alternative is to give more advance warning of cancellations so that the creators can
create a proper conclusion and tie up all the loose ends. My understanding is that cancellation notices are given half way of shooting through a season or something where all the stories are already planned and such.
*Insert negative stuff here.*
"..hiding your [story] beneath endless layers of confusion doesn’t make you an artist, it just makes people think you are."- Gameshadow