Half-Life VS. Mass Effect
"Over time, gameplay may fade but the stories and characters within these games lives on forever. Now, 32 of the most popular video game stories are trading blows in our Videogame Deathmatch for The Greatest Story Ever Told. Vote now and vote often to make sure your voice is heard so that your favorite game story can be crowned #1."
Commander Shepard, the first human Spectre, has been sent to Eden Prime to recover a Prothean beacon. Shepard is attacked by Saren, a rogue Specter, looking to unleash the power of Reapers, the same species that wiped out the Protheans 50,000 years prior.
Gordon Freeman awakes from stasis to learn Earth has been invaded by the Combine. Humanity's fate is in your hands, well humanity's fate is in your left hand, your right hand is holding a crowbar.
Pretty shit description of Half-Life if you ask me, but this is definitely a debatable match up.
Also up is Portal 2 vs. FF7.
Keep in mind this is ME1 vs. HL2