Doom: Demons are coming, kill them before they fuck up the worldWait, what? Doom's story is exactly this: "A gate to hell opens on Mars and demons appear. Kill them". And Halo's story: "Humans are at war against the Covenant, a conglomeration of several alien races following a religious prophecy that requires them to activate and fire the different halos spread around the galaxy/universe. Firing those halos will kill all sentient life in the galaxy, but they don't know it. The installations were setup by the Forerunners to destroy the Flood, a parasitic alien race that consumes all life forms. You are Master Chief Petty Officer Spartan 117, and you're thrown into the mix."
Halo: Aliens are inadvertantly going to fuck up the world, kill them.
Sure, the writers at bungie might have made the story more involved and interesting, but there is no denying that the base plot is still about killing aliens before they can fuck your shit up, which is exactly the same as Doom. iD just had a developer write their story, rather than a team of writers.