Half-Life is the best shooter. If you say Doom, I damn you to ♥♥♥♥♥♥♥ hell. Half-Life has big science facility with big awesome atmosphere and is totally immersive despite looking hilariously out-dated graphically. ok lemme put it this way; the plot is:

>I'm late
>Aspie coworkers screech at me
>Put on jumpsuit of shame
>Push rock into a machine
>phd in physics btw
>aliens start falling from the sky
>entire place explodes
>whoops lmao
>mass murdering aliens and employees
>genghis freeman
>cheers mate, the cavalry's here
>cavalry's shooting at me wtf
>conspiracy to get high score on scientists and nuke facility
>go into outerspace
>kill death metal album cover
>stop alien invasion lol
>kidnapped by guy with speech impediment
>get shoved in a locker lol

Yeah but it makes it all feel real and that's a big achievement. Play it. Do it. I'm watching you. Oh, great replayability btw. Especially when compared to other shooters.