Games that MUST be played.

[Jennacide]

Grim Fandango - Funniest game ever written.
Bioshock - Pure atmosphere and mood with great gameplay.
Amnesia: The Dark Descent - WILL MAKE YOU SHIT YOUR PANTS.
Bastion - The closest thing to perfection in years.
Portal 1 & 2 - A demonstration of great writing and gameplay.
System Shock 2 - Amazing and creepy RPG-shooter.
Deus Ex - The prototypical RPG-shooter.
Planescape: Torment - Best written game ever.

The last two didn't age horribly well, but there are some mods to fix stuff up and make them work/look better on modern machines, which helps greatly. They are still very much worth experiencing. Also, you may notice my utter love for all things Ken Levine. So might as well throw Thief onto that list too.

 

[dimensional]

The Longest Journey
Monkey Island 1 + 2
Baldurs gate 2
The Fools Errand

Thats all I can think of I usually stick to consoles although I have always wanted to play Vampire: the masquerade - Bloodlines its just now I have a pc that can run it I cant find it anywhere (except ebay obv).

 

[Cockney_Jesus]

Psychonauts.

No, it's not that you should play it because it's good, it's that you must buy it and play it or otherwise you're a dick. Anyone who has not bought that game should be ashamed of themselves, as it's philistines like you who are the reason why artful, fascinating and clever games aren't made.

^this x 10000000

 

[Cridhe]

A couple of my favorite PC games which still to this day remain untouched are Heroes of Might and Magic 2/3, and Jedi Outcast/Academy

Edit: Good lord I remember the days when I use to be a huge pot head and there's was nothing like some of the city music in HOMM to zone out to. Or the whurr-buzz-t'kch of a lightsaber that was amazing to look at.

 

[Cridhe]

Psychonauts.

No, it's not that you should play it because it's good, it's that you must buy it and play it or otherwise you're a dick. Anyone who has not bought that game should be ashamed of themselves, as it's philistines like you who are the reason why artful, fascinating and clever games aren't made.

Meh. It's just a 3D platformer, the story is more fun than the gameplay. 3D platformers are best left to consoles anyway and OP could just play it on a PS2.

 

[Fat Hippo]

Commander Keen

I don't know, Commander Keen is really brutal. Sure, it was one of the first big PC platformers, but I don't think it offers enough to a new gamer to be considered "Must Play."
And while I love my PC games, let's be honest: Mario is better. It can be hard too, sure, but CK can just be really fucking unfair.

 

[Davidline]

Every S.T.A.L.K.E.R unit out there for the amazing atmosphere and Gameplay when either modded or patched.

World of Warcraft...cough.

Age of Empires.

Doom.

Metal Slug, or Mortal Kombat. Probably both.

Mario, original.

 

[Racecarlock]

Battleships Forever. It's a top down tactical spaceship battle game that includes a shipmaker and room for custom sprites as well as weapons. Once you make your ship, you can modify HP for the hulls and the weapons along with weapon damage and range. You even have 4 different types of AI to choose from. The main game has a sandbox mode where you can spawn as many enemy, friendly, and player controlled ships as you want, whether they be massive or small, so you can have huge epic ship battles whenever you desire. Did I mention it's free? Get it now.

 

[Bloedhoest]

Oni, Command & Conqeur, Half Life, Shogo. Basically all the good old stuff.
Did I say you must play Oni?
Anyway, play Oni.

 

[Funkysandwich]

Commander Keen

I don't know, Commander Keen is really brutal. Sure, it was one of the first big PC platformers, but I don't think it offers enough to a new gamer to be considered "Must Play."
And while I love my PC games, let's be honest: Mario is better. It can be hard too, sure, but CK can just be really fucking unfair.

There's just some about Commander Keen that's so awesome though. I think most people should play it for about an hour, just to get an idea of what it's like. I played that game a lot when I was a kid, didn't make a whole lot of progress, but had a blast anyway.

 

[TheSharpie52]

Mass Effect 2 all the bloody way