Portal. 'nuff said.

Portal is good!

FPS: Killing Floor

Pros: Cheap, requires real teamwork

DOTA-Clone: League of Legends

Pros: Free!

Strategy: Supreme Commander, Sins of a Solar Empire

Pros: Both remakes of amazing games.

horror: Amnesia Dark Descent is a good one
platformer/indie: Super Meat Boy, Limbo
FPS: Half Life 2

+1 to Killing Floor

Portal is a blast, but I've found it has little-to-no replay value

Bioshock, on the other hand. I think I played that 2x and watched 2 other people play it all the way through.

I love strategy games, especially grand strategy games that take place over a long time on a large scale. My favourite is Europa Universalis III. Pick any country in the world from 1399 to 1821 and play it until 1821. Take charge of the economy, military, infrastructure, etc. etc. It's very detailed and extremely fun. You play as the kings or presidents or other leaders and it's only over if your country loses all provinces. You set your own goals, whether it's being rich or prestigious or conquering the world.

Dwarf Fortress is a dear love of mine. An extremely detailed sandbox world where you play a small colony of dwarves seeking to build a new home, turning it into a city and defending it against any number of invaders. The graphics of the game are in ASCII, but don't let that stop you. It's the most detailed game out there, every game has a vast randomly generated 3 world where every piece of stone has properties and a history. Like Minecraft but with a thousand times more detail. It's been in development for years and years and still growing, and it's free, living on donations.

It's a shame more people don't know about Killing Floor. It is hands-down the best Zombie shooter.

Bioshock is my favorite game ever. No other game comes close in terms of story telling and atmosphere. Phenomenal game. Just thinking about it makes me want to play it again. I just left it off here because I was thinking more computer exclusive titles.

endgame: singularity
master of orion 2
battle for wesnoth

and i dearly love baldur's gate 2

Dwarf Fortress has one of the hardest learning curves i've ever seen... i may have to pick it up again at some point... though i think it's more of a toy than a game.

Of course, BG2. And Battle for Wesnoth is really good. I especially love that I can play BfW natively in Linux. DF does indeed need hours and hours of learning before you can even survive for a year, but on the other hand it rewards you with weeks of entertainment. And blood, and guts. So much blood. So much magma. Blood.

I actually really enjoy Team Fortress 2. Also, Civizilation V and eagerly awaiting Diablo3. I have enjoied SWTOR but I can foresee my time on there lessening when Diablo 3 comes out.

If you like older computer games you should look at gog.com.

TF2 was a lot of fun, but I like it a lot less with all the customization. I think I'm just bitter because I played it for so long, then all of a sudden they introduced all these awards that didn't take into account all the stuff I'd already done.

Warcraft 3 and it's expanion The Frozen Throne.

I like TF2 atm cause it's free on Steam and can play with the hubby on it.

Civ iv player here. Waiting for the new computer to try civ v.

It's amazing. Not sure what I'll do if the expansion comes out at the same time Diablo 3 does. Both are number 1 and 2 on my games to get list.

Im not surprised to see that hardly anyone here plays Starcraft. A friend of mine tried to get me to play but I strongly prefer strategy games that are not all about click speed. My favorite fps so far is half life 2. I think I played it 3 times senior year of high school. It's a bit old now but man what a game...

Bioshock is pretty awesome.

But I have to say my favourite computer game ever might actually be Heroes of Might and Magic III. It's like 13 years old now, but it's still actually really great. I imagine someone else here must like turn based strategy...

Skyrim has broken RPG gaming for me. It is absolutely epic.

RTS clearly goes to SCII - again very far out of it's class.

In terms of best games for their time, I'd throw out a number of names already mentioned. But my list would be: Baldurs Gate II, Skyrim (Still a great game for its time), Heroes of Might and Magic, Conquest of the New World, and the Quest for Glory series.

Half life 2 was an amazing story, but i still rate half-life 1 as one of the best fps of all time, mostly for the sheer variety of gameplay...

Spore was one of the most addictive for me, but it lost its appeal after a month or so...

I also like Heroes of Might and Magic quite a lot - number 3's best, they ruined it a bit with number 4, but the newest ones are good.

Also, I've never played Skyrim, but Morrowind was an amazing game.

@orathaic in terms of variety of gameplay I'll have to give it to the grand theft auto franchise. Driving, shooting, missions, free to explore mode etc. on the whole perhaps one of the most engrossing worlds created for pc

Games I've obsessed over at various times in relatively recent history: Civ V, Mass Effect, Skyrim, Fallout 3, Dragon Age, GTA 4.

I love old-school games. Some of my favourites are Pacman, Space Harrier, Carrier Command, Bomb Jack. Retro joy.

Empire on the VAX computers was fun.
Gravity Wars, Bard's Tale and Lemmings on the Amiga was great.
The Perfect General on the Amiga was a blast when playing against another player via modem (LOL, a long time ago). Watching your artillery shell them was very satisfying.
Thief was a nice first person non shooter game better than any FPS.
Civ II, Civ III and Civ IV were enjoyable but having to learn the new wonders got tedious.
Ms Pacman for the retro games. Frogger for the PC was fun playing against others. Really enjoyed sitting on top of the other person as the truck roared down only to jump at the last second and watching them get squished.

Baldur's Gate is most likely the best I've ever played. Settlers of Catan (board game) on the computer is another good one.

Civilizations is always fun along with Medieval, Total War and Age of Empires. Age of Wonders (older game).

Baldur's Gate 2 and Star Control 2 were both amazing, deep games.

I love Skyrim too, but Morrowind had so much more content. Of course it's because there were no voice actors for the dialogue, but I'd rather have long scholarly theories on the disappearance of the dwarves than "I took an arrow in the knee" on repeat.