Half Life - Experiment goes wrong, makes a portal to another dimension, aliens everywhere, a lot of dead bodies, you are stuck in the middle, you meet some people who tries to help you, you try to make your way to the labs to find out how to fix the problem, you then travel to aliens homeworld and close the portal by knocking out the boss.
Doom 3 - Evil professor makes a portal to another dimension, demons everywhere, a lot of dead bodies, you are stuck in the middle, you meet very little people who tries to help you, you travel to the labs to find out what went wrong, you travel to hell to find the ultimate weapon, then come back to your world to close the final gate by destroying the boss.
IMO, I really think it's just a remake of Doom with a great atmosphere with a few added extras.