some times it is, some times it isn't. There's no one answer for all.
To work with cinematics you'd be best concentrating on animation. There was a time when people did everything in house but it's becoming more common to out-source it to a specialist like Blur Studios. They did the cinematics for Fable 2, they also did the Dawn of War games and recently they did the trailer for the Old Republic MMO.
It sounds like you may be more interested in-game cutscenes.