Was there a Dead Space movie about the guy who wakes you up at the beginning of Dead Space 2, and his sister, as they try to make it to Isaac Clarke?
You may be thinking of Dead Space: Aftermath
Dead Space: Aftermath is an American animated science fiction horror film that bridges the storyline between Dead Space and Dead Space 2.
The Overseer and his assistant watch a news report where Cho is accused of being a terrorist responsible for the Ishimura, Aegis VII colony, and O'Bannon disasters. They then discuss studying Stross, highlighting their luck in finding two people who have come into contact with the Marker. They proceed to store him in the lab where, in the slot next to him, is the other person - the crazed engineer that they found floating in a shuttle weeks ago who was responsible for destroying Aegis VII. The name of the engineer, Isaac Clarke, is then seen on a holographic monitor, marking the beginning of Dead Space 2
That's the only film that was released between the two games, and does not involved a sister. A slightly better match would be Dead Space: Ignition, an action puzzle game set as an interquel, and featuring Franco Delille and his partner Sarah (still not his sister), Franco being the one who wakes up Issac in Dead Space 2.
There were comic-book style cutscenes during the game: