Half Life. and Half-Life 2.
MIT Engineer Gordon Freeman takes a job at Black Mesa, a government research facility in New Mexico. During a test on a mysterious rock sample, he causes a resonance cascade which opens a portal between dimensions.
The result is a hostile alien race being unleashed in the facility. Unknown to the science team and security, the Marines are sent in to kill everyone and keep it queit. But they also underestimate the situation so Navy Seals deliver a Nuclear Device right before Gordon makes it out into the alternate dimension known as Xen. The mysterious G-man who follows your progress from afar then puts you into some sort of cryo-stasis.
In part 2, Gordon wakes up in an unknown european city, realising the events of Black Mesa were not contained and caused the apocalypse. He has no defined goal by the G-Man, but becomes a sort of savior of the survivors, who are now under the control of an advanced alien race. I know it sounds alittle odd, but if you've played the game, you know it kicks some serious ass.
Other games, Halo is obvious.
Starfox could be pretty cool for a video game flick, but anoher really really good one, would be The Legend of Zelda. Aim it at adults who played the originals for gameboy and NES and SNES even. Just don't cheapen it for younger kids.